drift: the #9399 sibling-guard pattern is live in four more places — fix the four, then remove the structure that generates them

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Summary

The audit found the same guard-drift pattern that #9399 fixed, still live in four more places. In each case a protection was added to the N instances someone grepped for, and the N+1th sibling — usually in the same file — was missed. This is a recurring class, not four coincidences, so the deliverables include a structural check as well as the four fixes.

The four live instances

1. Linked-issue satisfaction advisory has no commit-threshold cap (highest cost)

src/queue/processors.ts:8449's early-return set lacks commitThresholdReached. Both siblings have it — src/queue/slop-detection.ts:60,66 (via d66d17cea) and the ai_review path via focus-manifest.ts:205. Result: unbounded per-push LLM spend on long-lived PRs, at exactly the point where the other two advisory runners stop.

• Add the cap; assert all three advisory runners share one precondition set.

2. #9398's webhook-redelivery guard missed the panel-checkbox twins

#9398/#9399 established (same day) that the checkbox and text-command siblings must share redelivery guards. These four still lack it:

• maybeProcessPrPanelGenerateTests (processors.ts:14211) — the text twin has it at :13504-13505
• maybeProcessPrPanelRetrigger (:13995)
• maybeProcessGateOverrideCommand (:12906)
• maybeProcessResolveCommand (:13171)

A redelivered checkbox payload therefore re-pushes a second E2E test commit, re-runs a paid review, or re-writes an overridden check-run.

• Add delivery-id dedup to all four.

3. resolveCopycatDuplicateSibling open-state pre-filter present in 1 of 3 call sites

src/queue/duplicate-detection.ts:195 has it; duplicate-detection.ts:97 and src/rules/advisory.ts:1092 do not, and the callee documents the invariant as caller-owned (src/signals/copycat-duplicate.ts:32). advisory.ts has no downstream re-check, so a stale-cached-open, actually-merged sibling can mint a corroborated duplicate_pr_risk blocker.

• Apply the filter at all three call sites, or move it into the callee so it cannot be forgotten.

4. ai-slop-cache-input.ts fingerprint omits its own routing salt

src/queue/slop-detection.ts:137 swaps env.AI → env.AI_ADVISORY, but the fingerprint (src/review/ai-slop-cache-input.ts:20-29) carries only BYOK identity — null on the shared path. Flipping advisory_ai_routing.slop therefore replays the other model's cached advisory at an unchanged head. The rule it violates is written down in its own sibling (src/review/ai-review-cache-input.ts:65-69).

• Add the routing salt to the fingerprint. (Related: ai(cache): review fingerprint omits prompt and verdict-logic version — superseded verdicts replay forever (11 unbumped changes) #9477, the same class on the main review cache.)

Two more, lower severity

• @loopover review on a closed PR posts "Re-review triggered" and then no-ops (processors.ts:13253) — its two family members got this guard in orb(review): panel re-run checkbox on a closed/merged PR does real work, then silently no-ops #9020/queue: generate-tests checkbox and text-command both missing the pr.state !== "open" guard #9020 added to their retrigger sibling #9399.
• src/review/surface-disposition-reconciler.ts:79-90 lacks the requeue-interval guard its sweep-tick sibling has (src/review/pending-closure-watchdog.ts:87-94), so it can enqueue up to 200 redundant regate jobs per tick behind an unclaimable lock.

The structural fix (the actual point of this issue)

Fixing four siblings without changing the shape guarantees a fifth. Deliverables:

• Unify the command/panel handlers. There are ~9 slash-command and panel-checkbox handlers in processors.ts differing mainly in payload extraction. Put them behind one dispatch that owns state checks, redelivery dedup and rate limiting once. This structurally retires instance 2 and the closed-PR item.
• Unify the advisory spend gates. The three run*ForAdvisory runners should share one precondition struct (commit threshold, pause/freeze, mode, budget). Retires instance 1.
• Add a sibling-drift check. scripts/check-import-specifiers.ts is a working template. A check that flags "N call sites of X where M < N apply guard Y" is hard in general, but the specific high-value case — every handler in the command dispatch table declaring its guard set explicitly — is cheap once the dispatch exists.

Expected outcome

The four live drifts are closed, and the two structures that generate them (a 16k-line file of near-identical handlers, and three parallel advisory runners) stop being able to.

[linear-code]

JSO-6555