feat(profiles): make gitea.branch.delete a documented reconciler-owned capability

Merged-PR source-branch cleanup is reconciler work (task_capability_map maps
cleanup_merged_pr_branch -> reconciler / gitea.branch.delete), but the
reconciler profile schema, execution-profile docs, and tests never covered
the permission, so no configured profile could run the guarded
gitea_cleanup_merged_pr_branch path.

- reconciler_profile.py: add gitea.branch.delete to
  RECONCILER_RECOMMENDED_OPERATIONS (not required; not forbidden)
- docs/gitea-execution-profiles.md: document merged-branch cleanup
  ownership, least-privilege constraints, and the no-alias caveat
- tests/test_reconciler_profile.py: reconciler profile with branch.delete
  stays valid and classified reconciler; missing grant is reported as
  missing-recommended
- tests/test_branch_cleanup_guard.py: author- and merger-shaped profiles
  without gitea.branch.delete fail closed on gitea_cleanup_merged_pr_branch

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

tests/test_branch_cleanup_guard.py

@@ -93,6 +93,44 @@ class TestMergedPrBranchCleanupTool(unittest.TestCase):
         self.assertEqual(res["required_permission"], "gitea.branch.delete")
         self.mock_api.assert_not_called()
 
+    def test_author_and_merger_without_delete_authority_fail_closed(self):
+        role_profiles = {
+            "author": [
+                "gitea.read",
+                "gitea.branch.create",
+                "gitea.branch.push",
+                "gitea.repo.commit",
+                "gitea.pr.create",
+            ],
+            "merger": ["gitea.read", "gitea.pr.merge"],
+        }
+        for name, allowed in role_profiles.items():
+            with self.subTest(role=name):
+                profile_patch = patch(
+                    "mcp_server.get_profile",
+                    return_value={
+                        "profile_name": name,
+                        "allowed_operations": allowed,
+                        "forbidden_operations": [],
+                    },
+                )
+                profile_patch.start()
+                try:
+                    res = gitea_cleanup_merged_pr_branch(
+                        pr_number=487,
+                        confirmation="CLEANUP MERGED PR 487 BRANCH feat/branch",
+                        branch="feat/branch",
+                        remote="prgs",
+                        worktree_path="/tmp/repo/branches/cleanup",
+                    )
+                finally:
+                    profile_patch.stop()
+                self.assertFalse(res["performed"])
+                self.assertEqual(
+                    res["required_permission"], "gitea.branch.delete"
+                )
+                self.mock_api.assert_not_called()
+
     def test_root_checkout_cleanup_fails_closed(self):
         patch(
             "mcp_server.get_profile",