refactor(supervise): make Supervisor a service class the orchestrator calls

Turn the loose queue/audit functions in orchestrator/supervisor/queue.py into
methods on a concrete Supervisor service. The Orchestrator now owns an
injectable `self._supervisor` and calls `self._supervisor.write_proposal(...)`
etc., instead of module-level free functions — the supervise dependency is
explicit and mockable, and a Supervisor can be scoped to a `db_path` (defaults
to the host DB) so tests can point it at a temp database.

  - Supervisor (in the package __init__) drops the ABC and gains write_proposal,
    read_proposal, list_pending_proposals, list_all_pending_proposals,
    write_response, read_response, archive_all_proposals, write_audit_entry,
    read_audit_entries, plus the launch-time prepare().
  - render_diff / sha256_hex are pure and stateless, so they move to
    orchestrator/supervisor/util.py (re-exported from the facade) rather than
    becoming methods.
  - queue.py is deleted; service.py + the supervise tests call through a
    Supervisor instance.

Full unit suite green (2243).

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

tests/unit/test_orchestrator_control_plane.py

@@ -29,7 +29,7 @@ from bot_bottle.orchestrator.supervisor import (
     Proposal,
     TOOL_EGRESS_ALLOW,
     sha256_hex,
-    write_proposal,
+    Supervisor,
 )
 
 
@@ -421,7 +421,7 @@ class TestDispatchSupervise(unittest.TestCase):
         p = Proposal.new(
             bottle_slug=slug, tool=TOOL_EGRESS_ALLOW, proposed_file=proposed,
             justification="need it", current_file_hash=sha256_hex(proposed))
-        write_proposal(p)
+        Supervisor().write_proposal(p)
         return p.id
 
     def test_list_pending(self) -> None: