refactor(backend): rename consolidated_launch -> infra_launch (0081 review)

Mechanical rename addressing review 6141 on #519: "consolidated launch" was
unclear about what it composes. Rename the per-backend module
`consolidated_launch.py` -> `infra_launch.py` and the error
`ConsolidatedLaunchError` -> `InfraLaunchError` across all three backends and
their callers/tests. Unify the three identical per-backend error classes into
one `InfraLaunchError` defined in `backend/base.py` (re-exported by each
`infra_launch`) so the base backend can raise and catch a single shared type —
groundwork for the base owning the gateway-attach flow.

Add a glossary entry defining **infra** = the per-host gateway + orchestrator
service pair every bottle attaches to.

No behavior change.

Refs #516, #519.

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

bot_bottle/backend/docker/backend.py

@@ -142,5 +142,5 @@ class DockerBottleBackend(BottleBackend["DockerBottlePlan", "DockerBottleCleanup
         return _enumerate.enumerate_active()
 
     def attach_bottled_agents_to_gateway(self) -> None:
-        from .consolidated_launch import attach_bottled_agents_to_gateway
+        from .infra_launch import attach_bottled_agents_to_gateway
         attach_bottled_agents_to_gateway()