Add explicit close_pr capability resolution and gated PR close path (Issue #216)

PR closure had no first-class capability: agents could close PRs through
gitea_edit_pr(state=closed) with no close-specific capability proof, and
gitea_resolve_task_capability(close_pr) failed as unknown, leaving the
broad edit path as an untracked close fallback.

Add close_pr to the resolver TASK_MAP (gitea.pr.close, author-side) and
gate gitea_edit_pr(state=closed) on the same operation: without it the
close fails closed before any auth or API call, with reasons and a
structured permission_report; with it the close proceeds and is audited
as a distinct close_pr action carrying the required capability. Reject
invalid state values outright so case variants cannot bypass the gate.
Generalize the profile gate helper (_profile_operation_gate) and document
the PR comment / PR edit / PR close capability split.

Co-Authored-By: Claude Fable 5 <[email protected]>

tests/test_mcp_server.py

@@ -1621,7 +1621,8 @@ class TestTrackerHygieneCleanup(unittest.TestCase):
         self.mock_auth = patch("mcp_server.get_auth_header", return_value=FAKE_AUTH).start()
         patch("gitea_audit.audit_enabled", return_value=True).start()
         self.mock_audit = patch("gitea_audit.write_event").start()
-        patch("mcp_server.get_profile", return_value={"profile_name": "test", "allowed_operations": ["merge", "edit", "close"], "audit_label": "test", "forbidden_operations": []}).start()
+        # gitea.pr.close: closing a PR via gitea_edit_pr is capability-gated (#216).
+        patch("mcp_server.get_profile", return_value={"profile_name": "test", "allowed_operations": ["merge", "edit", "close", "gitea.pr.close"], "audit_label": "test", "forbidden_operations": []}).start()
 
     def tearDown(self):
         patch.stopall()