no-mistakes(document): Document already-returned worktree teardown recovery

Author: ruby-dlee

AGENTS.md

@@ -541,7 +541,8 @@ bin/fm-teardown.sh <id>
 ```
 
 The script refuses if the worktree holds uncommitted changes or committed work that has not landed; treat a refusal as a stop-and-investigate, not an obstacle.
-Teardown validates that the recorded project and worktree are exact roots with the expected repository registration, quiesces every ordinary task endpoint, and then runs the final non-destructive safety checks before any Treehouse return.
+Teardown normally validates that the recorded project and worktree are exact roots with the expected repository registration, quiesces every ordinary task endpoint, and then runs the final non-destructive safety checks before any Treehouse return.
+It can also finish bookkeeping for a provably landed worktree whose Treehouse lease was already cleared; `bin/fm-teardown.sh`'s header owns the fail-closed recovery contract.
 For a task whose metadata carries `report_required=1`, teardown also publishes the validated completion report before releasing the account lease or removing the worktree.
 A safety refusal after quiescence leaves the endpoint stopped while preserving all task state for repair and retry.
 `bin/fm-teardown.sh`'s header owns the full landed-work definition (remote-reachable, merged-PR-head containment for the squash-merge-then-delete-branch flow, content already in the default branch, local-only merges) and the `pr=` discovery fallback for merges that skipped `bin/fm-pr-check.sh`.

bin/fm-teardown.sh

@@ -29,6 +29,14 @@
 # Uncommitted changes are never landed.
 # Ordinary teardown first proves that metadata names the exact registered project,
 # worktree, and task lease, then quiesces the endpoint before its final safety checks.
+# If Treehouse already cleared that exact pool entry's lease, teardown treats the
+# worktree as a partial or completed external return only when the state has exactly
+# one matching entry, leased=false, no lease holder, and destroying is not true.
+# It then re-proves landed work under the checkout lock before completing the return
+# or cleaning the returned worktree, branch, and task bookkeeping. A missing
+# worktree directory is accepted only through the same cleared-lease proof and a
+# recovered task branch whose landed state can still be proved; ambiguous lease
+# state, branch lookup failure, and unlanded recovered work all retain task state.
 # Each locked Treehouse return repeats repository, lease, and landed-work checks
 # immediately before the destructive return command.
 # local-only projects additionally accept work merged into the local default