feat(author): add dirty-preserving same-claimant author-session rebind (Closes #864)

Introduce an explicit, fail-closed recovery operation that rebinds a live
author session to an already-registered dirty issue worktree when the durable
lock still belongs to the same identity/profile and the recorded owner PID is
provably dead. Ordinary locking remains clean-worktree-only; this path updates
only stale lock/session provenance, preserves every dirty byte under fingerprint
pins, and grants create-PR-sanctioned provenance without remote sync or recovery
worktrees.

Also stop treating dead-owner session pointers as live mutation workspace
bindings so a stale dead-owner pointer cannot poison unrelated author work.

task_capability_map.py

@@ -32,6 +32,17 @@ TASK_CAPABILITY_MAP: dict[str, dict[str, str]] = {
         "permission": "gitea.issue.comment",
         "role": "author",
     },
+    # #864: dirty-preserving same-claimant author-session rebind (dead owner PID).
+    # Author MCP tool path. Reconciler execute is gated inside the tool via
+    # authorize_reconciler_execute + role_kind checks (not this map entry).
+    "rebind_dirty_same_claimant_author_session": {
+        "permission": "gitea.issue.comment",
+        "role": "author",
+    },
+    "gitea_rebind_dirty_same_claimant_author_session": {
+        "permission": "gitea.issue.comment",
+        "role": "author",
+    },
     "set_issue_labels": {
         "permission": "gitea.issue.comment",
         "role": "author",