refactor(supervise): fold Supervise into the facade as Supervisor; drop dead flat-fallbacks

Move the `Supervise` lifecycle out of its own `orchestrator/supervisor/
supervise.py` and into the package `__init__`, renaming the class to
`Supervisor`. Callers now import it from `bot_bottle.orchestrator.supervisor`
alongside the queue surface it belongs with.

Remove the dead `try/except ImportError` flat-import fallbacks from the
package-only store modules (db_store, audit_store, config_store, queue_store)
and image_cache. Those fallbacks existed for when the store files were
flat-copied into the gateway; post-PRD-0070 the data plane never opens the DB,
so these modules are only ever imported as part of the package. The two gateway
data-plane files that may still be loaded flat (egress_addon_core,
git_gate_render) keep their fallbacks.

Full unit suite green (2251).

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

bot_bottle/supervisor/__init__.py

@@ -11,6 +11,6 @@ tier's private code, importable by `bot_bottle.gateway` **and**
     status / poll-status constants, and the shared daemon constants.
   * `plan`  — `SupervisePlan`, the launch-time staging DTO.
 
-The orchestrator-only half (queue I/O, diff rendering, the `Supervise`
+The orchestrator-only half (queue I/O, diff rendering, the `Supervisor`
 lifecycle) lives under `bot_bottle.orchestrator.supervisor`.
 """