feat(maestro): clear AwaitingInput glow once a pane has been focused

A session's rail glows AwaitingInput even after the operator has already
looked at it. Clients now report pane focus (POST /:id/focus); the daemon
clears the glow to Idle after 5s of continuous focus and keeps it cleared
until the session does new work, so a fresh Active cycle is required to
glow again.

web/src/api.ts

@@ -91,6 +91,22 @@ export async function killSession(id: Uuid, force = false): Promise<void> {
   );
 }
 
+/** Report whether this client's pane is the one currently showing `id` — not
+ * merely highlighted in a sidebar. The daemon uses this to clear an
+ * `AwaitingInput` glow once the pane has been looked at long enough
+ * (docs/SIDEBAR.md). Best-effort: a failure here only delays the glow
+ * clearing, so callers don't need to surface it. */
+export async function setSessionFocus(id: Uuid, focused: boolean): Promise<void> {
+  await jsonOrError(
+    await fetch(routes.sessionFocus(id), {
+      method: "POST",
+      credentials: "same-origin",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ focused }),
+    }),
+  );
+}
+
 /** List one directory's immediate subdirectories (NAP-329). `path` may be empty,
  * `~`, relative, or absolute — the daemon resolves it against its home dir. */
 export async function listDir(path: string): Promise<DirListing> {