fix(reviewer-workflow): address review — in-process mutation authority, no /tmp lock (#199)

Addresses the sysadmin REQUEST_CHANGES on PR #203 (reviewed head
10d2644790):

1. Lock redesigned; /tmp file removed entirely. The mutation authority is
   now an in-process record (_MUTATION_AUTHORITY) plus an environment
   session lock (GITEA_SESSION_PROFILE_LOCK) exported at server launch:
   - in-process record cannot be spoofed by other local processes, cannot
     go stale across sessions, and cannot race concurrent agents;
   - the env lock is inherited by child CLI processes, so review_pr.py can
     refuse an ad-hoc GITEA_MCP_PROFILE role escalation without any shared
     file; a missing env lock (direct operator CLI use) stays allowed;
   - silent except-pass writes are gone; an unresolvable profile fails
     closed.
2. Standard reviewer workflow unbroken: verify_mutation_authority seeds
   itself from the live config-resolved context at the first mutation gate
   (approved preflight path whoami -> eligibility -> review/merge), and now
   runs as the final gate after eligibility, reusing the identity that
   eligibility proved (no extra /user call).
3. Trailing whitespace removed from review_pr.py (git diff --check clean).
4. Module-global verify_mutation_authority no-op bypass removed from
   tests/test_mcp_server.py; replaced with a tests/conftest.py autouse
   fixture that only resets per-process state (_MUTATION_AUTHORITY,
   _IDENTITY_CACHE, session lock env) between tests — the gate itself
   stays live in every test.
5. Tests rewritten for the new design: seeding on first verify, unresolved
   profile fails closed, remote/profile/identity mismatches fail closed,
   session-lock env mismatch rejected, foreign-pid authority reseeded,
   unauthorized author->reviewer pivot blocked, authorized pivot allowed;
   CLI: mismatch blocked, match allowed, no-lock allowed.
6. Rebased onto current master (c6fd0fd).

Closes #199
Refs #194

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

tests/test_review_pr.py

@@ -112,39 +112,23 @@ class TestAPIPayload(unittest.TestCase):
 
 
 class TestMutationAuthorityLock(unittest.TestCase):
-    """Issue #194: verify that the CLI tool rejects profile overrides when mismatched with lock."""
+    """#199 (refs #194): the CLI refuses to run under a profile that differs
+    from the session profile lock exported by the launching MCP session."""
 
     @patch("review_pr.get_profile")
-    def test_cli_blocked_on_profile_mismatch(self, mock_get_profile):
+    def test_cli_blocked_on_session_lock_mismatch(self, mock_get_profile):
+        # An author-bound session exported the lock; the CLI resolves a
+        # reviewer profile (GITEA_MCP_PROFILE side-channel override) — reject
+        # before any API call.
         mock_get_profile.return_value = {"profile_name": "prgs-reviewer"}
-
-        original_exists = os.path.exists
-        def conditional_exists(path):
-            if "gitea_mutation_authority.lock" in str(path):
-                return True
-            return original_exists(path)
-
-        original_open = open
-        def conditional_open(file, *args, **kwargs):
-            if "gitea_mutation_authority.lock" in str(file):
-                return io.StringIO('{"current_profile": "prgs-author"}')
-            return original_open(file, *args, **kwargs)
-
-        from _pytest.monkeypatch import MonkeyPatch
         import io
         buf = io.StringIO()
-        monkeypatch = MonkeyPatch()
-        monkeypatch.setattr(sys, "stderr", buf)
-
-        with patch("os.path.exists", side_effect=conditional_exists), \
-             patch("builtins.open", side_effect=conditional_open):
-            try:
-                rc = review_pr.main([
-                    "--pr-number", "81", "--event", "APPROVE",
-                ])
-            finally:
-                monkeypatch.undo()
-
+        with patch.dict(os.environ,
+                        {"GITEA_SESSION_PROFILE_LOCK": "prgs-author"}), \
+             patch.object(sys, "stderr", buf):
+            rc = review_pr.main([
+                "--pr-number", "81", "--event", "APPROVE",
+            ])
         self.assertEqual(rc, 3)
         msg = buf.getvalue().lower()
         self.assertIn("cli override rejected", msg)
@@ -155,21 +139,22 @@ class TestMutationAuthorityLock(unittest.TestCase):
     def test_cli_allowed_on_profile_match(self, _auth, mock_api, mock_get_profile):
         mock_get_profile.return_value = {"profile_name": "prgs-reviewer"}
         mock_api.side_effect = [FAKE_PR_DATA, {}]
+        with patch.dict(os.environ,
+                        {"GITEA_SESSION_PROFILE_LOCK": "prgs-reviewer"}):
+            rc = review_pr.main([
+                "--pr-number", "81", "--event", "APPROVE",
+            ])
+        self.assertEqual(rc, 0)
 
-        original_exists = os.path.exists
-        def conditional_exists(path):
-            if "gitea_mutation_authority.lock" in str(path):
-                return True
-            return original_exists(path)
-
-        original_open = open
-        def conditional_open(file, *args, **kwargs):
-            if "gitea_mutation_authority.lock" in str(file):
-                return io.StringIO('{"current_profile": "prgs-reviewer"}')
-            return original_open(file, *args, **kwargs)
-
-        with patch("os.path.exists", side_effect=conditional_exists), \
-             patch("builtins.open", side_effect=conditional_open):
+    @patch("review_pr.api_request")
+    @patch("review_pr.get_auth_header", return_value=FAKE_CREDS)
+    def test_cli_allowed_without_session_lock(self, _auth, mock_api):
+        # No lock in the environment = direct operator CLI use; the wall
+        # does not apply and the normal flow proceeds.
+        mock_api.side_effect = [FAKE_PR_DATA, {}]
+        env = {k: v for k, v in os.environ.items()
+               if k != "GITEA_SESSION_PROFILE_LOCK"}
+        with patch.dict(os.environ, env, clear=True):
             rc = review_pr.main([
                 "--pr-number", "81", "--event", "APPROVE",
             ])