refactor(supervise): drop obsolete queue helpers (archive_proposal, wait_for_response, audit_dir/path)

Remove the supervise queue helpers that no live path uses anymore — they're
mechanisms the PRD-0070 / idempotent-poll migration superseded:

  - archive_proposal (+ QueueStore.archive_proposal): the poll stopped archiving
    on read (#469 review), so single-proposal archiving has no caller; decided
    proposals drop off the pending list via their response row and are reaped in
    bulk by archive_all_proposals on teardown/reconcile.
  - wait_for_response: the data plane polls the queue over the control-plane RPC
    now, so nothing block-waits on it.
  - audit_dir / audit_log_path: file-based audit paths, replaced by the SQLite
    AuditStore.

Also drops the tests that covered those obsolete helpers. Kept the prod-unused
read accessors list_pending_proposals and read_audit_entries: those aren't dead
mechanisms — they're the read side of live write paths that many tests use to
verify real queue/audit behavior.

Full unit suite green (2243).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/orchestrator/store/queue_store.py

@@ -167,25 +167,6 @@ class QueueStore(DbStore):
             raise FileNotFoundError(proposal_id)
         return self._row_to_response(row)
 
-    def archive_proposal(self, proposal_id: str) -> None:
-        if not self.db_path.is_file():
-            return
-        with self._connection() as conn:
-            conn.execute(
-                """
-                UPDATE supervise_proposals SET archived = 1
-                WHERE queue_key = ? AND id = ?
-                """,
-                (self.queue_key, proposal_id),
-            )
-            conn.execute(
-                """
-                UPDATE supervise_responses SET archived = 1
-                WHERE queue_key = ? AND proposal_id = ?
-                """,
-                (self.queue_key, proposal_id),
-            )
-
     def archive_all(self) -> None:
         """Archive every proposal + response for this queue key. Used to reap a
         bottle's supervise records when it is torn down or reconciled away —