[aft-alfonso]

Stacked on #1095 (needs its migrations 22-23; this adds migration 24). Retarget to main after #1095 merges.

When the 256-entry reliable-push retry buffer evicts a watch-match notice on a stalled connection, AFT records a durable gap. The next notice for that watch says, in the approved wording:

Some watch notices were lost: a stalled connection dropped 2 of them, and they cannot be recovered. At least 1 match is missing. Read the task output with bash_status({ task_id: "bash-gap", stderr_offset: 16 }).

("1 of them" for one notice; "Some matches may be missing." when matches can't be counted; OpenCode uses taskId/stderrOffset.) The gap is shown once, survives restart, follows the watch's exact-version acknowledgement, and never counts as a match for a one-shot watch. Health reports transport evictions separately from outstanding watch gaps and stays degraded until gaps are acknowledged. Recoverable snapshots and task completions are not counted as missing.

---

Summary by cubic

Shows a gap notice when a stalled connection drops watch-match notices, so the user learns that matches were lost and where to read the task output, and health stays degraded until the gap is acknowledged.

Migration

• Adds schema migration 24 with bash_watch_delivery_acks and bash_watch_delivery_gaps tables.

Behavior

• When the 256-entry reliable-push retry buffer evicts a watch-match notice, AFT records a durable gap; the next notice for that watch says how many notices and at least how many matches are missing, with a bash_status(...) pointer to the task output, or "Some matches may be missing" when matches cannot be counted.
• The gap shows once, survives restart, follows the watch's exact-version acknowledgement, and never counts as a match for a one-shot watch.
• Health reports transport evictions separately from outstanding watch gaps and stays degraded until gaps are acknowledged.
• Recoverable snapshots and task completions are not counted as missing.

^{Written for commit b6d5393. Summary will update on new commits.}