feat(spawn): share host spawn-pi mesh + models.json with spawned containers

- bind $LVMH_HOST_PI_RUNTIME_DIR/spawn-pi -> /root/.pi/spawn-pi (rw) so
  container pi's join the host pi's node mesh (spawn_pi/list_pi_nodes/
  send_pi_message now reach across the host/container boundary)
- bind host models.json (when present) over the stale image-baked
  fallback so newly added catalog models resolve in spawns

daemon/docker.go

@@ -47,11 +47,14 @@ const (
 	volumePiCache         string = "lvmh-pi-cache" // pi package cache (git:/npm:), shared across spawns
 	cacheMount            string = "/root/.pi/agent/cache"
 	authMountTarget       string = "/root/.pi/agent/auth.json"
+	modelsMountTarget     string = "/root/.pi/agent/models.json"
 	envHostPiAgentDir     string = "LVMH_HOST_PI_AGENT_DIR"
+	envHostPiRuntimeDir   string = "LVMH_HOST_PI_RUNTIME_DIR"
 	envSecretsDir         string = "LVMH_SECRETS_DIR"
 	envCloakCacheDir      string = "LVMH_CLOAK_CACHE_DIR"
 	envPlaywrightCacheDir string = "LVMH_PLAYWRIGHT_CACHE_DIR"
 	sshMountTarget        string = "/root/.ssh"
+	meshMountTarget       string = "/root/.pi/spawn-pi"
 	gitconfigMountTarget  string = "/root/.gitconfig"
 	workspaceMount        string = "/workspace"
 	sessionsMount         string = "/pi-sessions"
@@ -573,9 +576,24 @@ func (s *Spawner) createAndStart(ctx context.Context, repo, slug, model string,
 		volumePiCache+":"+cacheMount,
 	)
 	// Host pi credentials (OAuth tokens for anthropic etc.), read-only, so
-	// spawned agents can use every model the catalog offers.
+	// spawned agents can use every model the catalog offers. The host
+	// models.json rides along when present: image fallbacks are baked at
+	// build time and go stale the moment the dotfiles catalog changes.
 	if hostAgent := os.Getenv(envHostPiAgentDir); hostAgent != "" {
 		binds = append(binds, hostAgent+"/auth.json:"+authMountTarget+":ro")
+		if _, err := os.Stat(filepath.Join(hostAgent, "models.json")); err == nil {
+			binds = append(binds, hostAgent+"/models.json:"+modelsMountTarget+":ro")
+		}
+	}
+	// Shared spawn-pi mesh directory (node registry + AF_UNIX sockets),
+	// read-write: each pi creates its own socket and node file. Sharing it
+	// with the host puts container pi's on the same mesh as the host pi —
+	// without this each container is an isolated island.
+	if hostRuntime := os.Getenv(envHostPiRuntimeDir); hostRuntime != "" {
+		mesh := filepath.Join(hostRuntime, "spawn-pi")
+		if _, err := os.Stat(mesh); err == nil {
+			binds = append(binds, mesh+":"+meshMountTarget)
+		}
 	}
 	// Shared playwright browser cache (host path, read-only); the env var
 	// below makes every playwright-based MCP use it instead of downloading.

daemon/docker_test.go

@@ -519,6 +519,64 @@ func TestSpawnerSecretsBinds(t *testing.T) {
 	}
 }
 
+func TestWorkerBindsHostModelsJSON(t *testing.T) {
+	useFakeGit(t, fakeGitModeOK)
+	f := newFakeDocker()
+	sp, _ := newTestSpawner(t, f)
+	agent := t.TempDir()
+	if err := os.WriteFile(filepath.Join(agent, "models.json"), []byte(`{}`), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv(envHostPiAgentDir, agent)
+
+	res, err := sp.Start(context.Background(), "group/project", "", "", false)
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+	waitJobState(t, sp, res.SessionID, stateRunning)
+	creates := f.createsByName("lvmh-agent-")
+	binds := creates[0].HostConfig.Binds
+	want := agent + "/models.json:/root/.pi/agent/models.json:ro"
+	ok := false
+	for _, b := range binds {
+		if b == want {
+			ok = true
+		}
+	}
+	if !ok {
+		t.Fatalf("models.json bind missing from %v", binds)
+	}
+}
+
+func TestWorkerBindsSpawnPiMesh(t *testing.T) {
+	useFakeGit(t, fakeGitModeOK)
+	f := newFakeDocker()
+	sp, _ := newTestSpawner(t, f)
+	runtimeDir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(runtimeDir, "spawn-pi"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv(envHostPiRuntimeDir, runtimeDir)
+
+	res, err := sp.Start(context.Background(), "group/project", "", "", false)
+	if err != nil {
+		t.Fatalf("Start: %v", err)
+	}
+	waitJobState(t, sp, res.SessionID, stateRunning)
+	creates := f.createsByName("lvmh-agent-")
+	binds := creates[0].HostConfig.Binds
+	want := filepath.Join(runtimeDir, "spawn-pi") + ":/root/.pi/spawn-pi"
+	ok := false
+	for _, b := range binds {
+		if b == want {
+			ok = true
+		}
+	}
+	if !ok {
+		t.Fatalf("spawn-pi mesh bind missing from %v", binds)
+	}
+}
+
 func TestWorkerBindsCaches(t *testing.T) {
 	useFakeGit(t, fakeGitModeOK)
 	f := newFakeDocker()