Hidden CLI: l9 send / slim send — inject L9/SLIM wire traffic (dev/testing)

[juliarvalenti]

Summary

• Adds two hidden, undocumented CLI utilities for pushing crafted traffic onto a room's real SLIM channel — the git cat-file-style plumbing requested in Hidden CLI utilities: inject L9 payloads + raw SLIM messages into a room (dev/testing) #533, unblocking visual QA of the L9 Inspector (L9 inspector: expand a wire-feed row into full envelope JSON #501).
• mycelium l9 send --room R --as @handle --kind <kind> [--subkind <subkind>] [--data <json>] [...] — builds and publishes a hand-crafted L9 envelope.
• mycelium slim send --room R --as @handle --text "..." (or --json '{...}') — publishes an arbitrary raw message with no L9 semantics.

Changes

• mycelium.slim.member (new): ephemeral SLIM room membership — publish_once() joins a room as a given handle (asking the backend to invite it, the same call a resident connector makes on reconnect), waits to be admitted into the moderator's encrypted group, publishes one payload, and disconnects. This rides the real SLIM channel so the backend's own already-running persister/bus sees the traffic — a same-process shortcut (e.g. writing straight to the in-process bus from another process) can't reach it.
• mycelium.slim.l9: adds a generic build_envelope_content() supporting any kind/subkind (the existing build_reply_content() now delegates to it as the exchange-reply specialization), plus a VALID_SUBKINDS table mirroring the backend's app.services.l9.VALID_SUBKINDS, with validate_kind/validate_subkind run before anything touches the wire.
• mycelium.commands.wire (new): the two CLI commands, registered hidden=True and never @doc_ref'd, so they stay out of mycelium --help and the generated docs site. Each prints a runtime banner noting it bypasses the aligner and is for testing/demo only.
• contracts/slim-l9-wire.json: gains the frozen subkind table; both test_slim_l9_wire.py suites (backend + CLI) assert against it so the two copies can't silently drift.

Testing

• Unit tests pass (uv run pytest tests/ -x -q, both mycelium-cli and fastapi-backend)
• Linting passes (uv run ruff check .)
• Format check passes (uv run ruff format --check .)
• Type check passes (uv run ty check .)
• Added unit coverage: envelope construction against the wire contract (new + existing test_slim_l9_wire.py cases), kind/subkind validation (test_slim_l9.py), the join/publish sequence via the FakeSlimClient/fake_httpx fixtures (test_slim_member.py), and the CLI plumbing — hidden-from-help, validation-before-publish, envelope shape, --text/--json exclusivity (test_wire_cli.py).
• Not tested live against a running SLIM node / L9 Inspector (no node available in this environment) — the wire-contract and fake-transport tests cover the envelope shape and control flow; a live smoke test against the Inspector is still worth doing before closing out L9 inspector: expand a wire-feed row into full envelope JSON #501.

Related Issues

Closes #533

---

Generated by Claude Code