docs(agents): ADR 0019 unit checklist, owning-seam mock rule, worktree and rebase guidance

Retro follow-up (item 2). Adds docs/agents/adr-0019-unit.md — the order of
operations for one command unit with the declaration site for each step, the
evidence a unit review must carry, and what 'done' is not — so the pattern
rediscovered during the snapshot unit (#1779) is written down once.

testing.md: mock the seam the code under test consumes (fake inspectFacts /
bindDevice), not the generic dispatchCommand mock; a migrating command moves
its tests off the dispatch mock in the same PR.

AGENTS.md: fresh-worktree preflight (pnpm install + build in the worktree;
layering scan reads tracked files only) and concurrent-agent hygiene (one full
gate per host, verify subagent edits with git -C, one PR per worktree).

pull-requests.md: two readiness claims (published-and-reported vs merge-ready)
and the rebase rule — main has no up-to-date protection; rebase on conflict or
when `check:affected --base <merge-base> --head origin/main` names your surface.

Author: thymikee

AGENTS.md

@@ -14,6 +14,7 @@ situational lives one hop away — load it when the task calls for it.
 | Which gates to run, test speed rules, shared fixtures | `docs/agents/testing.md` |
 | Adding or changing a CLI flag | `docs/agents/cli-flags.md` |
 | Opening a PR, or reviewing one | `docs/agents/pull-requests.md` |
+| Migrating a command onto the request-bound platform runtime (an ADR 0019 unit) | `docs/agents/adr-0019-unit.md` |
 | Running commands against a real device | `docs/agents/device-verification.md` |
 | Issues, PRDs, triage labels | `docs/agents/issue-tracker.md`, `docs/agents/triage-labels.md` |
 | Web automation backend setup/diagnostics | `docs/agents/web-backend.md` |
@@ -160,6 +161,16 @@ one question so `rg` → read-whole-file stays one cheap bounded read.
   under `~/.agent-device/dev/<basename-slug>-<hash>`. Inspect with `pnpm daemon:state-dir`, override
   with `--state-dir`/`AGENT_DEVICE_STATE_DIR`, prune with `pnpm clean:daemon --prune-dev`. Daemons
   are isolated per worktree; **devices are not** — target different devices for concurrent worktrees.
+- A fresh worktree is not ready until `pnpm install --frozen-lockfile && pnpm build` ran **in it**.
+  Until then `@agent-device/*` and optional peers (`ai`) resolve against whichever checkout last
+  installed — typecheck fails on `src/ai-sdk`, and the smoke lanes fail with "Missing dist build".
+  Neither is a regression. The layering scan (`check:layering`) reads tracked files only, so an
+  untracked new module is invisible to it until `git add`.
+- Concurrent agents on one host: one full gate (`pnpm check`, `check:unit`) at a time — several
+  worktrees running unit suites together *are* the contention that produces timeout-shaped
+  failures. Verify a subagent's edits with `git -C <worktree> status/diff`, never from its report;
+  keep one PR per worktree and address PRs by URL/branch, not a number recalled from context;
+  give each agent its own scratch directory.
 - Node ≥22. Prefer built-ins (`fetch`, Web Streams, `AbortSignal.timeout`) over compatibility
   wrappers unless the surrounding code needs a lower-level transport.
 - Emit with `tsdown` (Rolldown), typecheck with TypeScript 7 via `tsc`. Declaration generation uses

docs/agents/adr-0019-unit.md

@@ -0,0 +1,64 @@
+# Migrating one command onto the request-bound platform runtime (ADR 0019 unit)
+
+The checklist for one command unit. ADR 0019 §6–10 holds the rules and the why; issue #1739 holds
+the wave plan and per-unit budgets; this file is the order of operations, with the seam, fixture,
+and gate you touch at each step. Everything here was rediscovered during the `snapshot` unit
+(#1779, 134 files) — do not rediscover it again.
+
+## Before writing code
+
+1. **Post the unit on #1739 first**: exact denominator (every inventory source or supported
+   device-runtime cell), parity source, facet owner, expected deletions, evidence tier
+   (request-scoped vs durable-resource), and the size budget. A unit without a posted budget has
+   no acceptance criterion; the late budget negotiation on #1779 is the incident.
+2. **One integration owner.** Parallel agents audit (platform parity, tests, size, architecture)
+   and implement only clearly disjoint lanes — a platform package's operations, a fixture builder,
+   the test migration. The shared spine — plan → facts → bind in the handler, the descriptor's
+   `platformExecution`, the cutover row — moves serially under one owner. Two agents editing the
+   spine produced the rebase churn on #1779.
+3. **Ask the owning-interface question before adding any gate**: "can this invariant be made
+   impossible at the seam (a type only one function can produce, a required parameter, one
+   construction path)?" If yes, do that; a cutover-row *extension* that recognizes a call shape is
+   the fallback, not the default, and it is what AGENTS.md's "reconstructing a compiler" principle
+   forbids once it needs a second omission patch.
+
+## The unit, in order
+
+Each step names its declaration site; read that, not prose.
+
+| Step | Where |
+| --- | --- |
+| Declare the use(s) with the one neutral `defineUse`; required-only by default, a preferred operation needs a recorded measurement in the unit review (§9) | `packages/contracts/src/platform-runtime-operations.ts` |
+| Plan resolution is pure and lives in contracts (`resolve<Command>RuntimePlan`), never in the handler | `packages/contracts/src/*-runtime-plan.ts` |
+| Handler: resolve plan → `inspectRequiredRuntimeUse(device, plan.use, inspectFacts)` → bind **once** with that use → operate. No admission-only binds, no `requireCommandSupported`, no capability bucket | `src/daemon/handlers/session-runtime-admission.ts`, the `snapshot` route in `src/daemon/snapshot-runtime.ts` as the model |
+| Descriptor flips to `platformExecution: { kind: 'device-runtime', use(s) }` in the same PR; the discriminator is exhaustive, so a forgotten descriptor fails typecheck | `src/core/command-descriptor/registry.ts` |
+| Each platform package reports exact-owner facts and implements the operations; provider ownership fails closed (missing behavior never falls through to a local owner) | `packages/platform-*/src/**`, `packages/provider-*/src/**` |
+| Add one row to the parametrized cutover table: `legacyRetirement` (what must be gone), `runtimeTypeNames`, `operations`, `singularExecution` with lexical `operationOwners`. The mechanism already carries the planted-red proof; a row that leaves a claim unstated is rejected by `cutoverRowDefects` | `scripts/layering/runtime-command-cutover-table.ts` (rule ids allocate upward; snapshot is R32) |
+| Delete: the legacy adapter, the descriptor's capability bucket + `requireCommandSupported` wiring, the retired route names — the row's `legacyRetirement` is the machine-checked list | wherever `legacyRetirement` points |
+| Tests: bind a fake runtime at the seam the handler consumes (`inspectFacts` / `bindDevice`), never a `dispatchCommand` mock. Move the command's existing tests off the dispatch mock in this PR | `src/daemon/__tests__/snapshot-runtime-fixture.ts` (fixture shape), `src/daemon/handlers/__tests__/session-command-harness.ts` (`mockInspectDeviceRuntimeFacts`, `mockBindDeviceRuntime`), `src/__tests__/test-utils/runtime-operation-facts.ts` (facts builders) |
+| Cross-cutting facets (freshness, system-chrome guard, presentation) land inside the first consuming unit and get one contract owner; later units consume, never fork | ADR 0019 §10 |
+
+## Evidence the unit review must contain
+
+- Request-scoped tier: the typed use declaration, fact coverage for every denominator cell, the
+  enumerated legacy-parity cell table, and the cutover-gate row. Durable-resource tier adds ADR
+  §4–5 lifecycle evidence. Importing durable machinery promotes the tier — say so.
+- Planted-red for anything new that is *not* a table row (a facet, a package boundary): revert,
+  run, quote the failing line. A row needs no planted-red of its own.
+- Size: root-bytes-removed vs package-bytes-added and the four checkpoint metrics
+  (`pnpm size --compare` against the base build), against the posted budget. Move-dominated is the
+  rule; net growth is itemized, not explained away.
+- Live evidence for the changed path on at least one real target per family the denominator
+  claims (`docs/agents/device-verification.md`); fixture-backed parity does not replace it.
+- Layering: `pnpm check:layering` green — R3 seam list narrows in the unit that removes an area's
+  last platform import and never grows; R9/R10 must not grow (`docs/agents/testing.md`).
+
+## What "done" is not
+
+- A migrated command with a legacy fallback, a provider/local fallback, or a `dispatchCommand`
+  branch left "just in case" — the row's retirement claim rejects it, and so does review.
+- Tests green because they mock the old seam. Grep the command's name across
+  `vi.mock('.../core/dispatch.ts')` users before calling the tail closed.
+- A per-command policy file in `scripts/layering/`. If the row's generalized columns cannot
+  express the invariant, first return to step 3; extensions are the exception and each one names
+  what the seam could not make impossible.

docs/agents/pull-requests.md

@@ -20,6 +20,27 @@
   bounded arrays in JSON, artifact paths for large raw data, progressive lookup for deeper detail.
 - Close every manual `agent-device` session opened during verification
   (`docs/agents/device-verification.md`) and report any cleanup that could not be completed.
+- Two readiness claims, never blurred: **published and reported** means the branch is pushed, the
+  PR body carries the evidence gathered at a named commit, and CI on the head is the authority
+  still to come; **merge-ready** means the required checks are green on the actual head and the
+  live evidence for the changed path exists. "Don't wait for CI" licenses the first, not the
+  second — say which one you are claiming.
+
+## Rebasing onto a moving `main`
+
+`main` has no "require branches up to date" rule; a rebase is not owed to GitHub. Rebase when
+there is a conflict, or when the commits `main` gained since your base touch a surface your
+change depends on or that decides your gates:
+
+```sh
+pnpm check:affected --base <your-merge-base> --head origin/main   # what main gained, by gate
+```
+
+If that plan names only files and gates disjoint from yours, the rebase buys nothing but another
+full validation cycle. Evidence in the PR body is stamped with the commit it was gathered at, so a
+rebase dates it rather than invalidating it, and CI on the new head re-establishes it. A merge
+queue is the answer once independent migration units regularly land against each other; until
+then this rule is.
 
 ## PR body
 

docs/agents/testing.md

@@ -78,6 +78,16 @@ cleanup for a directory they created — that's the global teardown's job, and p
 already existed for other reasons should stay (it's the fallback global sweep that's new, not a
 replacement for tests being tidy).
 
+Mock the seam the code under test consumes, not the widest one available. A daemon handler that
+binds a device runtime is tested by handing it a fake `inspectFacts` / `bindDevice` (the fixture
+shape in `src/daemon/__tests__/snapshot-runtime-fixture.ts`; the shared mocks in
+`src/daemon/handlers/__tests__/session-command-harness.ts`; facts builders in
+`src/__tests__/test-utils/runtime-operation-facts.ts`) — not by `vi.mock('.../core/dispatch.ts')`.
+The generic dispatch mock is for tests *of* dispatch. Sixty-odd files still mock it from before
+the runtime seam existed; retiring `dispatchCommand('snapshot')` surfaced them one failure at a
+time. Do not add to that set, and when a command migrates (`docs/agents/adr-0019-unit.md`), its
+tests move to the runtime seam in the same PR.
+
 Keep tests behavioral. Do not assert shapes or cases TypeScript already proves.
 
 A test added as a regression pin must be shown to fail without the change it pins — vacuity is the