refactor: extract supervise types to _supervise_types, eliminate get_supervise_mod()

Proposal, Response, AuditEntry, host_db_path, bot_bottle_root, and their
shared constants/helpers are moved to a new _supervise_types.py module.
queue_store and audit_store now import these directly instead of deferring
through get_supervise_mod() at call time.

host_db_path() in _supervise_types uses sys.modules[__name__].bot_bottle_root()
so monkey-patches on _supervise_types.bot_bottle_root propagate through it.
supervise.host_db_path() is re-defined to call bot_bottle_root() through
supervise's own globals, preserving patchability for callers that go through
the supervise module.

Test fixtures that create stores without an explicit db_path now patch
_sv_types.bot_bottle_root alongside supervise.bot_bottle_root. The server
test patches both flat and package _supervise_types since handle_tools_call
runs in the package context while the responder thread uses the flat module.

Dockerfile.sidecars gets a COPY for _supervise_types.py so the sidecar
bundle retains its flat import chain.

Follow-up to issuecomment-2872 on PR #320.

tests/unit/test_supervise_cli.py

@@ -12,6 +12,7 @@ from pathlib import Path
 from unittest.mock import patch
 
 from bot_bottle import supervise
+from bot_bottle import _supervise_types as _sv_types
 from bot_bottle.audit_store import AuditStore
 from bot_bottle.cli import supervise as supervise_cli
 from bot_bottle.queue_store import QueueStore
@@ -54,13 +55,20 @@ class _FakeHomeMixin:
 
     def _setup_fake_home(self):
         self._tmp = tempfile.TemporaryDirectory(prefix="supervise-test.")
-        original = supervise.bot_bottle_root
+        original_sv = supervise.bot_bottle_root
+        original_svt = _sv_types.bot_bottle_root
 
         def fake_root() -> Path:
             return Path(self._tmp.name) / ".bot-bottle"
 
         supervise.bot_bottle_root = fake_root  # type: ignore[assignment]
-        self._restore_home = lambda: setattr(supervise, "bot_bottle_root", original)
+        _sv_types.bot_bottle_root = fake_root  # type: ignore[assignment]
+
+        def restore() -> None:
+            supervise.bot_bottle_root = original_sv  # type: ignore[assignment]
+            _sv_types.bot_bottle_root = original_svt  # type: ignore[assignment]
+
+        self._restore_home = restore
         QueueStore("").migrate()
         AuditStore().migrate()