refactor(yuanbao): drop dead branch A1 message_id loop + pin missing fixture

PR #29211 review findings:

1. test_retry_replacement: pin DEFAULT_DB_PATH so SessionDB() doesn't write
   to the real ~/.hermes/state.db. Same fix as the other DB-only fixtures.

2. yuanbao recall branch A1 (message_id exact match) was structurally dead
   once load_transcript() became DB-only — state.db never preserves the
   platform message_id. Removed the dead loop, consolidated to a single
   content-match branch (renamed 'A: content match'). Branch B (system
   note) unchanged. Updated the test name + docstring to reflect this.

Note: self._lock is no longer taken in append_to_transcript (was guarding
the JSONL file append). SQLite append_message handles its own concurrency
via WAL mode, so this is safe; flagging for awareness.

gateway/platforms/yuanbao.py

@@ -1410,32 +1410,24 @@ class RecallGuardMiddleware(InboundMiddleware):
             logger.warning("[%s] Recall: failed to resolve session: %s", adapter.name, exc)
             return
 
-        # Load transcript from canonical store (state.db).
-        #
-        # Branch A1 below tries to match the recalled message by its platform
-        # `message_id`. state.db does NOT preserve `message_id` (only its own
-        # autoincrement primary key), so A1 will not match for any message
-        # persisted post-DB-canonical (i.e. all messages going forward). Recall
-        # falls through to A2 (content match) or B (system redaction note), both
-        # of which work DB-only.
-        #
-        # TODO: add a `platform_message_id` column to state.db messages to restore
-        # exact-id matching. Tracked separately.
+        # Load transcript from canonical store (state.db). See Branch A below
+        # for why we can no longer match by platform `message_id`.
         try:
             transcript = store.load_transcript(sid)
         except Exception as exc:
             logger.warning("[%s] Recall: failed to load transcript: %s", adapter.name, exc)
             return
 
-        # Branch A: redact — try message_id first, then content fallback.
-        # Observed messages have message_id; agent-processed @bot messages
-        # only have content (run.py doesn't write message_id to transcript).
+        # Branch A: content-match redaction. state.db does NOT preserve the
+        # platform `message_id` (only its own autoincrement primary key), so we
+        # cannot redact by exact id. Match by content instead. Most yuanbao
+        # recalls carry the recalled text via `recalled_content`, which is
+        # sufficient for any non-duplicate message.
+        #
+        # TODO: add a `platform_message_id` column to state.db messages to
+        # restore exact-id matching. Tracked separately.
         target = None
-        for entry in transcript:
-            if entry.get("message_id") == recalled_id:
-                target = entry
-                break
-        if target is None and recalled_content:
+        if recalled_content:
             for entry in transcript:
                 if entry.get("role") == "user" and entry.get("content") == recalled_content:
                     target = entry
@@ -1444,7 +1436,7 @@ class RecallGuardMiddleware(InboundMiddleware):
             target["content"] = cls._REDACTED
             try:
                 store.rewrite_transcript(sid, transcript)
-                logger.info("[%s] Recall: redacted msg_id=%s (branch A)", adapter.name, recalled_id)
+                logger.info("[%s] Recall: redacted msg_id=%s (branch A: content match)", adapter.name, recalled_id)
             except Exception as exc:
                 logger.warning("[%s] Recall: rewrite_transcript failed: %s", adapter.name, exc)
             return

tests/gateway/platforms/test_yuanbao_recall_db_only.py

@@ -1,10 +1,10 @@
-"""Yuanbao recall: branch A2 (content-match) works without JSONL message_id."""
+"""Yuanbao recall: branch A (content-match) works against DB-only transcripts."""
 from gateway.session import SessionStore
 from gateway.config import GatewayConfig
 
 
-def test_recall_falls_through_to_content_match_without_message_id(tmp_path, monkeypatch):
-    """When transcript has no message_id field, A2 content-match still works.
+def test_recall_content_match_finds_target_in_db_transcript(tmp_path, monkeypatch):
+    """state.db doesn't preserve message_id, so recall uses content-match.
 
     Pin DEFAULT_DB_PATH to tmp_path so SessionDB() can't write to the real
     ~/.hermes/state.db. (Module-level constant snapshot, see test_load_transcript_db_only.)
@@ -20,12 +20,11 @@ def test_recall_falls_through_to_content_match_without_message_id(tmp_path, monk
     store.append_to_transcript(sid, {"role": "user", "content": "sensitive content", "timestamp": 1.0})
     store.append_to_transcript(sid, {"role": "assistant", "content": "ack", "timestamp": 2.0})
 
-    # The post-PR state: load_transcript returns DB-only, no message_id field.
+    # DB-only history carries no platform message_id (PR #29211 dropped that path).
     history = store.load_transcript(sid)
-    assert all("message_id" not in msg for msg in history), \
-        "DB-only history should not carry message_id"
+    assert all("message_id" not in msg for msg in history)
 
-    # Branch A2: content match should still find the message
+    # Branch A: content match finds the target row that recall would redact.
     target = next((m for m in history
                    if m.get("role") == "user" and m.get("content") == "sensitive content"), None)
     assert target is not None

tests/gateway/test_retry_replacement.py

@@ -11,7 +11,12 @@ from gateway.session import SessionStore
 
 
 @pytest.mark.asyncio
-async def test_gateway_retry_replaces_last_user_turn_in_transcript(tmp_path):
+async def test_gateway_retry_replaces_last_user_turn_in_transcript(tmp_path, monkeypatch):
+    # Pin DEFAULT_DB_PATH so SessionDB() doesn't write to the real ~/.hermes/state.db.
+    # (Module-level constant snapshot, see test_load_transcript_db_only.)
+    import hermes_state
+    monkeypatch.setattr(hermes_state, "DEFAULT_DB_PATH", tmp_path / "state.db")
+
     config = GatewayConfig()
     store = SessionStore(sessions_dir=tmp_path, config=config)