feat(maestro): spawn form defaults command to claude + prefills cwd to daemon home dir (NAP-328)

Two web spawn QoL improvements plus the wire support they need:

- Command field now prefills `claude` instead of an empty box.
- Working directory prefills the selected daemon's home dir, updating on
  daemon change unless the user has typed their own value.

The daemon resolves its `$HOME` via `dirs::home_dir()` at startup and
advertises it end-to-end: a new `home_dir` field on `DaemonOutbound::Hello`
flows through the registry's `register` into `DaemonInfo` (served on
`/api/daemons` and `/api/events`). The field is `#[serde(default)]`, so older
daemons that omit it deserialize to an empty string — backward compatible, and
the UI simply skips prefill when it's empty.

Hierarchical `/`-separated labels in the web sidebar already worked
(web/src/catalog.ts); no change there.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/spawn.ts

@@ -25,7 +25,7 @@ export function openSpawnModal(daemons: Map<string, DaemonInfo>): void {
         </label>
         <label>
           Command
-          <input name="command" type="text" required placeholder="bash" autocomplete="off" />
+          <input name="command" type="text" required value="claude" placeholder="bash" autocomplete="off" />
         </label>
         <label>
           Name (optional)
@@ -82,6 +82,21 @@ export function openSpawnModal(daemons: Map<string, DaemonInfo>): void {
     }
   }
 
+  // Prefill the working directory with the selected daemon's home dir, and keep
+  // it in sync when the daemon changes — unless the user has typed their own.
+  const cwdInput = host.querySelector("input[name=cwd]") as HTMLInputElement;
+  let cwdEdited = false;
+  cwdInput.addEventListener("input", () => {
+    cwdEdited = true;
+  });
+  const applyHomeDir = () => {
+    if (cwdEdited) return;
+    const home = daemons.get(select.value)?.home_dir;
+    if (home) cwdInput.value = home;
+  };
+  select.addEventListener("change", applyHomeDir);
+  applyHomeDir();
+
   const close = () => host.remove();
   host.querySelector(".close")?.addEventListener("click", close);
   host.querySelector(".cancel")?.addEventListener("click", close);

web/src/types.ts

@@ -22,6 +22,9 @@ export interface DaemonInfo {
   hostname: string;
   version: string;
   daemon_url: string;
+  /** Home dir of the user the daemon runs as; used to prefill the spawn form's
+   * working directory. Empty/absent for older daemons. */
+  home_dir?: string;
 }
 
 export interface WorktreeSpec {