feat(supervise): provision agent-side MCP config so Claude sees the sidecar

The supervise sidecar (PRD 0013) has been serving MCP at
http://supervise:9100/ since it landed, but the in-bottle Claude
Code had no `.mcp.json` or settings pointing there — so the agent
couldn't actually call cred-proxy-block / pipelock-block /
capability-block as tools. To exercise the flow you had to curl
the sidecar from a sibling container.

This closes that last mile.

- claude_bottle/backend/docker/provision/supervise.py (new):
  provision_supervise(plan, target) writes
  ~/.claude/settings.json into the running agent container with an
  mcpServers.supervise entry of type http pointing at the
  per-bottle sidecar. No-op when bottle.supervise is False.
- BottleBackend.provision orchestrator gains provision_supervise as
  the last step (after CA, prompt, skills, git, cred-proxy). Default
  impl is a no-op so non-Docker backends aren't forced to implement it.
- DockerBottleBackend wires it through to the new module.
- Test covers the rendered settings shape so a future regression in
  the MCP entry format would surface in unit-level CI.

To test the full flow end-to-end now:
  ./cli.py start <agent> --cwd       # agent's claude sees supervise
  # agent calls cred-proxy-block via MCP
  ./cli.py dashboard                  # approve
  ./cli.py resume <identity>          # restart with new capabilities

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

claude_bottle/backend/__init__.py

@@ -229,6 +229,7 @@ class BottleBackend(ABC, Generic[PlanT, CleanupT]):
         self.provision_skills(plan, target)
         self.provision_git(plan, target)
         self.provision_cred_proxy(plan, target)
+        self.provision_supervise(plan, target)
         return prompt_path
 
     def provision_ca(self, plan: PlanT, target: str) -> None:
@@ -263,6 +264,13 @@ class BottleBackend(ABC, Generic[PlanT, CleanupT]):
         Default impl is a no-op for backends that don't yet support
         the cred-proxy sidecar; the Docker backend overrides."""
 
+    def provision_supervise(self, plan: PlanT, target: str) -> None:
+        """Write the in-bottle Claude Code MCP config so the agent
+        discovers the per-bottle supervise sidecar (PRD 0013).
+        No-op when bottle.supervise is False or the backend doesn't
+        support the supervise sidecar yet. The Docker backend
+        overrides."""
+
     @abstractmethod
     def prepare_cleanup(self) -> CleanupT:
         """Enumerate orphaned resources from previous bottles. No side