fix(pi): close routine stale wake acknowledgment gap

[withally]

Intent

Fix the Pi supervision branch so routine identical stale wake offers are never accepted and forgotten: preserve bounded coalescing, defer one normal durable-queue recheck after the active eligible-row snapshot settles, acknowledge any remaining branch-owned row, leave already-consumed rows as an empty no-op, and cover both boundaries without changing wake-drain, wake-grant, parent stall detection, or fm_branch_report.

What Changed

• Track identical stale: offers received while a branch turn’s eligible-row snapshot is in flight, then perform one normal durable-queue recheck after the turn settles, with generation and shutdown cleanup.
• Extend Pi supervision documentation and regressions to cover stale rows arriving before and after the snapshot, including remaining-row acknowledgment and already-consumed empty no-op behavior.

Risk Assessment

✅ Low: The patch is narrowly scoped to serialized stale-wake bookkeeping and covers both pre- and post-snapshot boundaries without changing the owned drain, grant, watcher, or report paths.

Testing

The target passes bounded coalescing, post-snapshot durable recheck, branch acknowledgement, consumed-row no-op, wake-drain, wake-grant, parent-stall, fm_branch_report, and real-Pi-SDK checks. The worktree is clean and reviewer-visible CLI evidence is captured.

Evidence: Pi branch routine stale-wake evidence

Source: Pi branch routine stale-wake evidence

Target boundary passed; base reproduced timeout at deferred acknowledgement; real Pi SDK 0.84.2 passed; preserved contract files unchanged.

Pi supervision routine stale-wake boundary evidence
target=8494a17dd4fc9b90bdba248132c45136e6de3f6a
base=95b76889d0f4497251f6a5896de370ba6d604e88
target_boundary_status=0
ok - Pi branch coalesces routine floods, bypasses urgent delay, and rechecks post-snapshot stale rows
base_boundary_status=1 (expected non-zero regression)
not ok - Pi branch must recheck an accepted identical stale row after the current snapshot settles: <anonymous_script>:214
  throw new Error(`timed out waiting for ${label}`);
        ^

Error: timed out waiting for deferred acknowledgement for the post-snapshot duplicate
    at settle (eval at <anonymous> �[90m(file://~/.no-mistakes/worktrees/37852af5566c/01M1BY8767NGWFHAZHAD7GE982/�[39m[eval1]:2:7), <anonymous>:214:9�[90m)�[39m
    at async �[90mfile://~/.no-mistakes/worktrees/37852af5566c/01M1BY8767NGWFHAZHAD7GE982/�[39m[eval1]:92:1

Node.js v24.20.0: expected exit 0, got 1
real_sdk_status=0
ok - real Pi SDK 0.84.2 accepts the branch session construction and preserves an unpromptable wake
ok - real Pi SDK 0.84.2 applies an explicit branch model on create and over a reopened session's recorded model
ok - real Pi SDK 0.84.2 reports its own supported effort levels and applies an explicit branch effort over a reopened session's recorded level
ok - real Pi SDK 0.84.2 delivers a custom message to the provider as user text carrying only content, so the captain outcome's typed envelope is what reaches the model
preserved_contract_files=unchanged

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

✅ **Review** - passed

✅ No issues found.

✅ **Test** - passed

✅ No issues found.

• bash tests/fm-pi-branch-extension.test.sh
• bash tests/fm-wake-queue.test.sh
• FM_PI_BRANCH_LIVE_E2E=1 bash tests/fm-pi-branch-live-e2e.test.sh
• bash tests/fm-branch-supervision.test.sh
• Focused test_branch_coalesces_repeat_wakes_and_bypasses_for_urgent_work against target and base extension implementations

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.