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/docker/provision/supervise.py

@@ -0,0 +1,75 @@
+"""Supervise sidecar provisioning inside a running Docker bottle
+(PRD 0013).
+
+Writes ~/.claude/settings.json with an `mcpServers.supervise` entry
+pointing at the per-bottle supervise sidecar so the in-bottle Claude
+Code discovers the three stuck-recovery MCP tools (cred-proxy-block,
+pipelock-block, capability-block) at startup.
+
+No-op when bottle.supervise is False — bottles that haven't opted
+into the supervise sidecar shouldn't get an MCP entry pointing at a
+sidecar that isn't running.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import subprocess
+
+from ....log import info
+from ....supervise import SUPERVISE_HOSTNAME, SUPERVISE_PORT
+from .. import util as docker_mod
+from ..bottle_plan import DockerBottlePlan
+
+
+_AGENT_HOME_DEFAULT = "/home/node"
+_SETTINGS_REL_PATH = ".claude/settings.json"
+_SUPERVISE_MCP_NAME = "supervise"
+
+
+def render_settings() -> str:
+    """The settings.json content the agent reads on startup. Stable
+    shape — only the URL is parameterized in case CLAUDE_BOTTLE_*
+    env overrides change the supervise hostname/port someday."""
+    cfg = {
+        "mcpServers": {
+            _SUPERVISE_MCP_NAME: {
+                "type": "http",
+                "url": f"http://{SUPERVISE_HOSTNAME}:{SUPERVISE_PORT}/",
+            },
+        },
+    }
+    return json.dumps(cfg, indent=2) + "\n"
+
+
+def provision_supervise(plan: DockerBottlePlan, target: str) -> None:
+    """Drop ~/.claude/settings.json into the running agent container
+    when bottle.supervise is True. No-op otherwise."""
+    if plan.supervise_plan is None:
+        return
+
+    container_home = os.environ.get(
+        "CLAUDE_BOTTLE_CONTAINER_HOME", _AGENT_HOME_DEFAULT,
+    )
+    settings_in_container = f"{container_home}/{_SETTINGS_REL_PATH}"
+    settings_dir_in_container = settings_in_container.rsplit("/", 1)[0]
+
+    host_path = plan.stage_dir / "agent_claude_settings.json"
+    host_path.write_text(render_settings())
+    host_path.chmod(0o644)
+
+    info(f"writing {settings_in_container} (supervise MCP server entry)")
+    # The Dockerfile creates ~/.claude.json at the top of HOME but
+    # not the ~/.claude/ subdir, so make sure it exists before cp.
+    docker_mod.docker_exec_root(target, ["mkdir", "-p", settings_dir_in_container])
+    subprocess.run(
+        ["docker", "cp", str(host_path), f"{target}:{settings_in_container}"],
+        stdout=subprocess.DEVNULL,
+        check=True,
+    )
+    docker_mod.docker_exec_root(target, ["chown", "-R", "node:node", settings_dir_in_container])
+    docker_mod.docker_exec_root(target, ["chmod", "644", settings_in_container])
+
+
+__all__ = ["provision_supervise", "render_settings"]