fix(mcp): require visible APPROVED reviews before merge (closes #244)

Gitea expects review event APPROVED, not APPROVE; the wrong event left
submissions as PENDING drafts. Verify terminal verdicts after submit,
submit pending drafts when needed, and block merge when approval_visible
is false.

tests/test_audit.py

@@ -293,9 +293,12 @@ class TestGatedToolAudit(_AuditWiringBase):
     @patch("mcp_server.api_request")
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_merge_success_audited(self, _auth, mock_api):
-        # user, pr, merge POST, readback — no extra identity call (uses result).
+        # user, pr, feedback pr+reviews, merge POST, readback.
         mock_api.side_effect = [
             {"login": "merger-bot"}, self._pr("author-bot"),
+            self._pr("author-bot"),
+            [{"id": 1, "user": {"login": "reviewer-bot"}, "state": "APPROVED",
+              "submitted_at": "2026-07-06T10:00:00Z", "dismissed": False}],
             {}, {"merged_commit_sha": "c1"},
         ]
         env = self._env(GITEA_PROFILE_NAME="gitea-merger",
@@ -332,7 +335,10 @@ class TestGatedToolAudit(_AuditWiringBase):
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_submit_review_success_audited(self, _auth, mock_api):
         mock_api.side_effect = [
-            {"login": "reviewer-bot"}, self._pr("author-bot"), {"id": 7},
+            {"login": "reviewer-bot"}, self._pr("author-bot"),
+            {"id": 7, "state": "APPROVED"},
+            [{"id": 7, "user": {"login": "reviewer-bot"}, "state": "APPROVED",
+              "submitted_at": "2026-07-06T10:00:00Z", "dismissed": False}],
         ]
         env = self._env(GITEA_PROFILE_NAME="gitea-reviewer",
                         GITEA_ALLOWED_OPERATIONS="read,review,approve")