fix(hindsight): availability probe must cover the embedding stack for local modes

_check_local_runtime() only imported 'hindsight' and
'hindsight_embed.daemon_embed_manager', a strictly weaker import surface
than the embedded daemon actually needs: the daemon imports
sentence_transformers at startup (embeddings + reranker). When the
embedding stack is broken (e.g. a dependency conflict on a shared package
like huggingface-hub), the daemon can never start, yet is_available() and
'hermes memory status' still report Hindsight as available — every
retain/recall then fails silently.

Import sentence_transformers in the same probe so local/local_embedded
availability goes red with the real ImportError as the reason, letting
the agent degrade loudly instead of silently dropping memory. Local path
only; cloud mode is untouched and no network or model download is
triggered by the import.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MN8RMDLwxCfFxwtADoEJJf

plugins/memory/hindsight/__init__.py

@@ -131,10 +131,19 @@ def _check_local_runtime() -> tuple[bool, str | None]:
     error from NumPy before the daemon starts. Treat that as "unavailable"
     so Hermes can degrade gracefully instead of repeatedly trying to start
     a broken local memory backend.
+
+    The embedded daemon computes embeddings via ``sentence_transformers``
+    (transformers + huggingface-hub). Importing ``hindsight`` /
+    ``hindsight_embed`` alone succeeds even when that stack is broken, so
+    without importing it here the probe would falsely report the backend
+    healthy and ``hermes memory status`` would stay green while the daemon
+    aborts at startup on every retain/recall. Import it too so the probe (and
+    status) reports the real ImportError.
     """
     try:
         importlib.import_module("hindsight")
         importlib.import_module("hindsight_embed.daemon_embed_manager")
+        importlib.import_module("sentence_transformers")
         return True, None
     except Exception as exc:
         return False, str(exc)