fix(sessions): leave a pending idle alert to the user through a keep-alive turn

Only a human spends an idle alert, but the keep-alive turn resolved an unseen one three ways: its working transition, its stop hook, and its own idle prompt replacing the item with a pre-acknowledged one. While the turn runs, a pending idle item is now left exactly as found, the page's stop handler returns on the keep-alive reason before clearing hooks or raising Response Complete, and session:working/session:idle carry keepAlive so the stuck-detection timer neither restarts nor re-arms.

The window that marks the turn closes on its own idle prompt or any other submit instead of a fixed three minutes, which a slow turn's idle prompt (sent a minute after the turn ends) could outlast. The service keeps the default and cap in memory, read through a strict reader so a mid-write read is retried rather than kept, and the cap is clamped before the strict settings save.

src/session.ts

@@ -456,6 +456,15 @@ export interface ClaudeMessage {
   duration_ms?: number;
 }
 
+/**
+ * Whether a programmatic write leaves the keep-alive turn running: the nudge itself, or a bare
+ * Enter (which submits nothing new). Anything else carrying an Enter starts a turn of its own.
+ */
+function isKeepAliveWrite(data: string): boolean {
+  const text = data.replace(/[\r\n]/g, '').trim();
+  return text === '' || text === KEEP_WARM_NUDGE;
+}
+
 /**
  * Event signatures emitted by the Session class.
  * Subscribe using `session.on('eventName', handler)`.
@@ -1562,8 +1571,10 @@ export class Session extends EventEmitter {
   /**
    * True while the running turn is Codeman's own keep-alive nudge: its stop hook and idle
    * prompt open pre-acknowledged, and its submit moves `lastSubmitAt` (it IS a submit, and the
-   * response viewer's conversation correlation needs it) but not `lastRealPromptAt`. Any
-   * `fromUser` write ends it early, so a person's prompt right after a nudge counts and alerts normally.
+   * response viewer's conversation correlation needs it) but not `lastRealPromptAt`. The turn's
+   * own idle prompt ends it (`endKeepAliveTurn()`), and so does any other submit: a `fromUser`
+   * write, a programmatic write of anything but the nudge, or a `prompt_submitted` hook for
+   * another prompt, so a prompt right after a nudge counts and alerts normally.
    */
   get keepAliveTurnActive(): boolean {
     return Date.now() < this._keepAliveTurnUntil;
@@ -1573,6 +1584,10 @@ export class Session extends EventEmitter {
     this._keepAliveTurnUntil = Date.now() + windowMs;
   }
 
+  endKeepAliveTurn(): void {
+    this._keepAliveTurnUntil = 0;
+  }
+
   /** Last keystroke a person sent (`fromUser` write), epoch ms; 0 when none this process. */
   get lastHumanInputAt(): number {
     return this._lastHumanInputAt;
@@ -4741,6 +4756,9 @@ export class Session extends EventEmitter {
       this._lastHumanInputAt = Date.now();
       // A person is here: whatever turn follows is theirs, not the keep-alive's.
       this._keepAliveTurnUntil = 0;
+    } else if (hasEnter && !isKeepAliveWrite(data)) {
+      // Anything else submitted (an agent, respawn, auto-resume) starts a turn of its own.
+      this._keepAliveTurnUntil = 0;
     }
     if (hasEnter) this._stampSubmit();
     return submitted;