feat(profiler): wire BEHAVE-SHELL extraction onto attacker.session.ended

The profiler worker now consumes attacker.session.ended on the bus
AND walks unprofiled session_recorded log rows on every tick. Both
paths converge on a single handler that:

1. Validates required payload fields (session_id, decky_id, service,
   attacker_ip, shard_path).
2. Builds evidence_ref shard:{decky}/{service}/{shard_basename}#{sid}
   and skips when has_observations_for_evidence is True (idempotent
   re-runs).
3. Resolves attacker_uuid via get_attacker_uuid_by_ip; defers if the
   profiler tick hasn't materialised the row yet.
4. Reads the asciinema shard, slices events for the sid, calls
   extract_session, persists each Observation via upsert_observation
   (per-row; batch transaction filed as follow-up), then publishes
   each on the bus best-effort (fire-and-forget per DEBT-029 §6).

Architecture:
* Handler lives in decnet/profiler/behave_shell/_handler.py — pure
  function, unit-tested in isolation.
* Worker.py adds _behave_pump (queue feed), _drain_behave_queue
  (per-tick drain), _behave_poll_tick (cursor scan over
  session_recorded logs), and _payload_from_log_row (Log → bus-shape
  payload projection).
* Poll cursor uses a separate state key
  (attacker_worker_session_cursor) so the correlation tick's cursor
  doesn't conflate.
* has_observations_for_evidence promoted to BaseRepository abstract.

22 new tests across handler / drain / poll layers covering happy
path, all skip paths, isolation against handler exceptions,
idempotency on re-run, and cursor key separation. TTP worker bus
tests still green — payload field is purely additive.

Closes BEHAVE-INTEGRATION.md Phase 4.

decnet/web/db/repository.py

@@ -341,6 +341,16 @@ class BaseRepository(ABC):
         ordered by ``ts`` ASC. Empty list when none."""
         raise NotImplementedError
 
+    @abstractmethod
+    async def has_observations_for_evidence(self, evidence_ref: str) -> bool:
+        """True iff any observation row carries this ``evidence_ref``.
+
+        Worker uses this as the "have we already profiled this session?"
+        check before kicking the BEHAVE-SHELL extractor — equivalent
+        to "is this ``(decky, service, sid)`` already in the table?".
+        """
+        raise NotImplementedError
+
     async def upsert_observed_attachment(
         self,
         *,