fix(orchestrator): address review on host control server transport (#468)

Codex review on #496:

- **High — ambiguous delivery no longer orphans a launched bottle.** A
  timeout / dropped response from the host controller is now the ambiguous
  BrokerUnavailableError (distinct from the definite BrokerAuthError /
  BrokerClientError). OrchestratorCore.launch_bottle keeps the registry
  row on the ambiguous case instead of deregistering — deregistering would
  orphan a running container with no record (reconcile reaps rows, never
  containers). The row is left for reconcile to reap iff the bottle is not
  actually live. Definite failures still roll back, so a real failure
  leaves no orphan row.
- **Medium — the privileged endpoint bounds request bodies.** The host
  server rejects an oversized Content-Length with 413 before reading it,
  and sets a per-request socket timeout, so a caller that can merely reach
  the socket (no signed token) can't exhaust memory or a handler thread.

Tests: ambiguous-keep vs definite-rollback in the launch path; the
BrokerUnavailableError/BrokerClientError split in BrokerClient; the 413
body cap + handler error paths (driven in-thread, since daemon request
threads lose coverage) plus a deterministic real-socket check that
declares an oversized Content-Length but sends a sliver (rejection on the
header, no unread-body reset race); and the __main__ entrypoint broker
selection. Diff-coverage 98%; pyright clean; pylint 9.8.

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

bot_bottle/orchestrator/broker.py

@@ -38,7 +38,21 @@ _ALLOWED_OPS = ("launch", "teardown")
 class BrokerAuthError(Exception):
     """A broker request failed provenance or schema verification —
     bad/absent signature, malformed token, or a payload that doesn't match
-    the fixed launch-request shape. Fail-closed: the broker must not act."""
+    the fixed launch-request shape. Fail-closed: the broker must not act.
+
+    A **definite** negative: nothing was launched, so a caller may safely roll
+    back as if the op never happened."""
+
+
+class BrokerUnavailableError(Exception):
+    """A brokered request could not be carried to a verdict: the broker (or the
+    wire to it) was unreachable, timed out, or dropped the response.
+
+    Crucially **ambiguous** — unlike `BrokerAuthError`, the op MAY already have
+    taken effect on the backend before the response was lost, so a caller must
+    NOT assume it did nothing (e.g. must not roll a registry row back as if no
+    launch happened, which would orphan a running container). Only the in-process
+    brokers never raise this; the out-of-process `BrokerClient` does."""
 
 
 @dataclass(frozen=True)
@@ -179,6 +193,7 @@ class StubBroker(LaunchBroker):
 
 __all__ = [
     "BrokerAuthError",
+    "BrokerUnavailableError",
     "LaunchRequest",
     "SubmitBroker",
     "LaunchBroker",