fix(state): quarantine SessionDB handle after structural corruption

A bare SQLITE_CORRUPT/NOTADB on a live write (not FTS-scoped, not a
replaced file) now sets a sticky per-instance flag: later writes fail
fast with StateDbCorruptError, the handle never reopens after close(),
and close() skips its explicit PASSIVE WAL checkpoint. Gateway and agent
flush paths divert pending transcripts to JSONL/spool like the replaced
case instead of retrying forever.

Field evidence: a handle that kept writing for ~50 minutes after the
first structural error checkpointed 15 pages under the wrong page
numbers on shutdown (page 1 <- messages_fts_trigram_data leaf), turning
"malformed" into "file is not a database".

Refs #90837, #90950, #97940, #89332, #45383

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CNX8rNYHqA5pT4tAGSzXtb

run_agent.py

@@ -2670,13 +2670,17 @@ class AIAgent:
             # ("storage was busy, send it again") from disk-full/read-only.
             from hermes_state import (
                 CompressionSessionClosedError,
+                StateDbCorruptError,
                 StateDbReplacedError,
                 classify_persistence_error,
                 divert_session_transcript_jsonl,
             )
 
             self._last_persistence_error_cause = classify_persistence_error(e)
-            if isinstance(e, StateDbReplacedError):
+            if isinstance(e, (StateDbReplacedError, StateDbCorruptError)):
+                # Replaced generation or quarantined (structurally corrupt)
+                # handle: SQLite will not take this batch again, so keep it
+                # on disk instead of only in RAM.
                 try:
                     divert_session_transcript_jsonl(
                         getattr(self, "session_id", "") or "",
@@ -2684,7 +2688,8 @@ class AIAgent:
                     )
                 except Exception:
                     logger.warning(
-                        "JSONL divert failed after state.db replace for %s",
+                        "JSONL divert failed after state.db %s for %s",
+                        self._last_persistence_error_cause,
                         getattr(self, "session_id", None),
                         exc_info=True,
                     )