claude-code: register the agent's configuration at three scopes, served as the nox-mesh plugin

Skills, subagents, commands and hooks had no machine-wide place, so they were
copied into homes by hand and drifted. Each is now registered once through the
module's tools, kept in its config state, and written per node: the plugin in
the managed directory, settings and instructions in the managed files, or the
account's own directory, touching only what the module placed. hq ADR 0216.

modules/claude-code/cmd/claude-code/main.go

@@ -30,6 +30,9 @@ func say(format string, args ...any) {
 // writeManaged writes one managed file as root, only when its content changed. From a staged file, never
 // /dev/stdin: a child's input may be a socket, which /dev/stdin cannot open (found on the first assignment).
 func writeManaged(name, content string) (string, error) {
+	if strings.HasSuffix(name, "/") {
+		return writeManagedTree(strings.TrimSuffix(name, "/"), content)
+	}
 	path := filepath.Join(ManagedDir, name)
 	if was, err := os.ReadFile(path); err == nil && string(was) == content {
 		return name + ": unchanged", nil
@@ -54,6 +57,74 @@ func writeManaged(name, content string) (string, error) {
 	return name + ": written", nil
 }
 
+// writeManagedTree replaces one directory of the managed directory whole — the plugin's marketplace (ADR
+// 0216) — when what it holds differs from the files given (a JSON map of path to PluginFile). Staged
+// beside, then swapped in as root, so a session never reads half of it.
+func writeManagedTree(name, content string) (string, error) {
+	var files map[string]PluginFile
+	if err := json.Unmarshal([]byte(content), &files); err != nil {
+		return "", err
+	}
+	target := filepath.Join(ManagedDir, name)
+	if sameTree(target, files) {
+		return name + "/: unchanged", nil
+	}
+	staged, err := os.MkdirTemp("", "claude-code-tree-")
+	if err != nil {
+		return "", err
+	}
+	defer os.RemoveAll(staged)
+	for rel, f := range files {
+		full := filepath.Join(staged, filepath.FromSlash(rel))
+		if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
+			return "", err
+		}
+		mode := os.FileMode(0o644)
+		if f.Executable {
+			mode = 0o755
+		}
+		if err := os.WriteFile(full, []byte(f.Content), mode); err != nil {
+			return "", err
+		}
+		_ = os.Chmod(full, mode)
+	}
+	_ = os.Chmod(staged, 0o755)
+	script := `set -e; rm -rf "$2.next" "$2.old"; cp -r "$1" "$2.next"; chown -R root:root "$2.next"; chmod -R go-w,a+rX "$2.next";
+if [ -d "$2" ]; then mv "$2" "$2.old"; fi; mv "$2.next" "$2"; rm -rf "$2.old"`
+	args := []string{"sh", "-c", script, "sh", staged, target}
+	if os.Geteuid() != 0 {
+		args = append([]string{"sudo", "-n"}, args...)
+	}
+	if out, err := exec.Command(args[0], args[1:]...).CombinedOutput(); err != nil {
+		return "", fmt.Errorf("%s/: could not be written to %s (%s); the module writes there through the operator account's passwordless sudo",
+			name, ManagedDir, strings.TrimSpace(string(out)))
+	}
+	return fmt.Sprintf("%s/: written, %d file(s)", name, len(files)), nil
+}
+
+// sameTree says whether a directory holds exactly these files, with these contents and executable bits.
+func sameTree(dir string, files map[string]PluginFile) bool {
+	found := 0
+	err := filepath.WalkDir(dir, func(full string, d os.DirEntry, err error) error {
+		if err != nil || d.IsDir() {
+			return err
+		}
+		rel, _ := filepath.Rel(dir, full)
+		f, ok := files[filepath.ToSlash(rel)]
+		if !ok {
+			return errors.New("not wanted")
+		}
+		raw, err := os.ReadFile(full)
+		info, ierr := d.Info()
+		if err != nil || ierr != nil || string(raw) != f.Content || (info.Mode()&0o111 != 0) != f.Executable {
+			return errors.New("differs")
+		}
+		found++
+		return nil
+	})
+	return err == nil && found == len(files)
+}
+
 // ask is a tool on the bus, through the runtime: its answer is the tool's value.
 func ask(address string, args any) (json.RawMessage, error) { return stdio.Ask(address, args) }
 
@@ -63,6 +134,13 @@ type stateOf struct{ s stdio.KeptState }
 func (s stateOf) Put(key string, value any) error { _, err := s.s.Put(key, value); return err }
 func (s stateOf) Delete(key string) error         { return s.s.Delete(key) }
 func (s stateOf) Keys() ([]string, error)         { return s.s.Keys() }
+func (s stateOf) Get(key string) (json.RawMessage, bool, error) {
+	e, err := s.s.Get(key)
+	if err != nil || e == nil {
+		return nil, false, err
+	}
+	return e.Value, true, nil
+}
 
 // nodesRunningMe is the nodes claude-code runs on, from the controller's list of modules — for the register
 // tool's question.
@@ -152,9 +230,9 @@ func nodesOf(v any) []string {
 	return out
 }
 
-func tools(p Paths, servers ServerState, view *ServerView) []stdio.Tool {
+func tools(p Paths, servers ServerState, view *ServerView, config ConfigState, configView *ConfigView) []stdio.Tool {
 	nodesArg := str(`more nodes: "all" for every node running claude-code, or a comma-separated list; absent is this node only`)
-	return []stdio.Tool{
+	out := []stdio.Tool{
 		{Name: "claude_code_status",
 			Description: "Claude Code on this machine as the mesh configured it: the licence it holds and when its token expires, what it reports holding, the managed files, the MCP servers registered here. Fingerprints only, never a token.",
 			Run:         func(map[string]any) (any, error) { return status(p), nil }},
@@ -239,6 +317,7 @@ func tools(p Paths, servers ServerState, view *ServerView) []stdio.Tool {
 				return RegisterServer(p, Registration{Name: name, Nodes: nodesOf(a["nodes"])}, servers, view, writeManaged, nodesRunningMe)
 			}},
 	}
+	return append(out, configTools(p, config, configView)...)
 }
 
 // persist asks the state again until it answers: its bucket or the bus's grant may arrive after the module.
@@ -283,15 +362,44 @@ func main() {
 	}
 	servers := stateOf{stdio.State("servers")}
 	view := NewServerView(p)
-	go run(p, view)
-	if err := stdio.Serve("", tools(p, servers, view)); err != nil {
+	config := stateOf{stdio.State("config")}
+	configView := NewConfigView(p)
+	go run(p, view, configView)
+	if err := stdio.Serve("", tools(p, servers, view, config, configView)); err != nil {
 		say("%v", err)
 		os.Exit(1)
 	}
 }
 
 // run is the module's long-running half, beside the tools (ADR 0198).
-func run(p Paths, view *ServerView) {
+func run(p Paths, view *ServerView, configView *ConfigView) {
+	// The agent's configuration, at every scope (ADR 0216): the whole current set first, then each change.
+	go persist("watching the agent's configuration", func() error {
+		return stdio.State("config").Watch("", func(c stdio.StateChange) error {
+			var item *Item
+			if c.Op == "put" {
+				item = &Item{}
+				if json.Unmarshal(c.Value, item) != nil {
+					item = nil
+				}
+			}
+			if !configView.Take(c.Key, c.Op, item) {
+				return nil
+			}
+			if out, err := RenderNow(p, writeManaged); err != nil {
+				say("taking %s %s: %v", c.Op, c.Key, err)
+			} else {
+				say("took %s %s", c.Op, c.Key)
+				for _, line := range out {
+					if !strings.HasSuffix(line, "unchanged") {
+						say("%s", line)
+					}
+				}
+			}
+			return nil
+		})
+	}, func(n int) { say("watching the agent's configuration%s", refusals(n)) })
+
 	// Every node's MCP servers: the whole current set first, then each change (ADR 0201).
 	go persist("watching the MCP servers", func() error {
 		return stdio.State("servers").Watch("", func(c stdio.StateChange) error {