perf(webui/session-load-latency) tier4: fix CI failures — lint B009/B905 + _emit_slow format args

Three fixes for the CI failures (lint + test shard 1):

1. B009 lint fix (api/routes.py:6281): Replace getattr(session, 'profile')
   with session.profile — the guard on line 6275 already ensures it exists.

2. B905 lint fix (api/routes.py:13843): Add strict=True to zip() of
   _draft_stages slices. Both sides are always the same length (shifted
   by one), so strict=True is correct.

3. _emit_slow format-arg fix (api/request_diagnostics.py:186-195):
   Keep the prefix in the format string and pass the JSON payload as a
   separate positional argument. The test at
   test_issue1855_request_diagnostics.py:33 does
   json.loads(caplog.records[0].args[0]) and the old code embedded the
   prefix in the payload string, breaking the JSON parse. Now
   self.logger.warning("%s %s", prefix, payload) — wait, actually
   self.logger.warning(f"{prefix} %s", payload) — so args[0] is the
   raw JSON string, same as the pre-_emit_slow code.

api/request_diagnostics.py

@@ -184,15 +184,16 @@ class RequestDiagnostics:
             self._current_stage_started = now
 
     def _emit_slow(self, prefix: str, record: dict) -> None:
-        payload = f"{prefix} {json.dumps(record, sort_keys=True)}"
+        payload = json.dumps(record, sort_keys=True)
+        log_msg = f"{prefix} %s"
         if self._print_fn is not None:
             try:
-                self._print_fn(payload)
+                self._print_fn(log_msg % payload)
             except Exception:
                 # print_fn is best-effort; never break a request thread.
                 pass
         else:
-            self.logger.warning("%s", payload)
+            self.logger.warning(log_msg, payload)
 
     def finish(self) -> None:
         record = None

api/routes.py

@@ -6278,7 +6278,7 @@ def _read_profile_model_config(
     try:
         from api.profiles import get_hermes_home_for_profile
 
-        _profile_name = str(getattr(session, "profile") or "")
+        _profile_name = str(session.profile or "")
         _profile_home = get_hermes_home_for_profile(_profile_name)
         _profile_cfg_path = os.path.join(str(_profile_home), "config.yaml")
         if not os.path.isfile(_profile_cfg_path):
@@ -13840,7 +13840,7 @@ def handle_post(handler, parsed) -> bool:
         if _draft_stages[-1][1] - _draft_t0 > 0.2:
             parts = " ".join(
                 f"{n}={((t - prev[1]) * 1000):.1f}ms"
-                for (n, t), prev in zip(_draft_stages[1:], _draft_stages[:-1])
+                for (n, t), prev in zip(_draft_stages[1:], _draft_stages[:-1], strict=True)
             )
             handler._safe_webui_print(
                 "[SLOW] /api/session/draft total=%.1fms stages: %s" % (