fix(state): SessionDB open waits out a lock lost inside the FTS constructor

In rollback-journal (DELETE) mode a sibling process can take the write lock
between schema load and the messages_fts probe. FTS5's xConnect then fails its
%_config read and SQLite reports SQLITE_BUSY with the text "vtable constructor
failed: messages_fts". Every state.db lock classifier matched on the words
"locked"/"busy", so:

- a writable SessionDB() failed after 1s instead of waiting out the lock with
  _WRITE_PATIENCE_S, and callers disabled persistence for the run;
- a read-only open (dashboard, `hermes sessions list`, cross-profile readers)
  failed on the first busy timeout with no retry at all;
- the error read as not transient (dashboard 500, not 503) and as persistence
  cause "unknown" instead of "locked".

Add hermes_state_errors.is_sqlite_lock_error: SQLITE_BUSY/SQLITE_LOCKED by
result code when SQLite supplies one, text only when it does not (our own
re-raised messages, RPC-wrapped strings). Route the writer open patience loop,
the _execute_write retry, the reconcile re-raise, the WAL->DELETE flip, the
maintenance holder probe, is_transient_sqlite_error and
classify_persistence_error through it. The read-only open retries a lock
inside its existing bounded retry budget, next to the transient IOERR case.

hermes_state_holders.py

@@ -15,6 +15,8 @@ import sys
 from pathlib import Path
 from typing import Callable, List, Optional, Sequence, Set, Tuple
 
+from hermes_state_errors import is_sqlite_lock_error
+
 try:  # Hard dependency, but tolerate scaffold-phase imports before pip install.
     import psutil
 except ImportError:  # pragma: no cover - stripped/scaffold installs only
@@ -536,8 +538,7 @@ def live_writer_holds_db(
         probe.execute("ROLLBACK")
         return False
     except sqlite3.OperationalError as exc:
-        lowered = str(exc).lower()
-        return "locked" in lowered or "busy" in lowered
+        return is_sqlite_lock_error(exc)
     except sqlite3.DatabaseError:
         # Malformed/unreadable with no holder on the scan: nobody else has it open, so repair may run.
         return False