Fix false stall detection for multi-article chained generation

The frontend status poller measured elapsed time from `started` (set once
at the beginning of the run) and declared a stall at 300s.  Three articles
take ~6 minutes total, so the poller always false-alarmed on article 3.

Now every stage broadcast writes `last_updated` into the transient, and
the stall check compares idle time since the last update — not since the
run started.  This lets N-article runs complete without false timeout as
long as each individual article finishes within 5 minutes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/class-executor.php

@@ -108,6 +108,7 @@ class PRAutoBlogger_Executor {
 			'status'       => 'running',
 			'stage'        => __( 'Starting generation...', 'prautoblogger' ),
 			'started'      => time(),
+			'last_updated' => time(),
 		], self::STATUS_TTL );
 
 		// Schedule immediate one-shot cron event. WordPress will fire this
@@ -190,11 +191,7 @@ class PRAutoBlogger_Executor {
 		}
 	}
 
-	/**
+	/** Cron handler: process next queued article. Chained by Pipeline_Runner. */
-	 * Cron handler: process the next queued article in its own PHP process.
-	 *
-	 * Chained by Pipeline_Runner — each article gets its own execution time.
-	 */
 	public function on_process_article_queue(): void {
 		// phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
 		@ignore_user_abort( true );
@@ -249,8 +246,10 @@ class PRAutoBlogger_Executor {
 				}
 			}
 
-			// After 5 min with no progress, declare failure.
+			// Stall = 5 min since last stage update (not since start).
-			if ( $elapsed > 300 ) {
+			$last_activity = $status['last_updated'] ?? $status['started'] ?? 0;
+			$idle_seconds  = time() - $last_activity;
+			if ( $idle_seconds > 300 ) {
 				$this->abort_orphaned_run( __( 'Generation stalled. Check Activity Log.', 'prautoblogger' ) );
 				return;
 			}
@@ -276,6 +275,7 @@ class PRAutoBlogger_Executor {
 		$current = get_transient( self::STATUS_TRANSIENT );
 		if ( is_array( $current ) ) {
 			$current['stage']        = $stage;
+			$current['last_updated'] = time();
 			set_transient( self::STATUS_TRANSIENT, $current, self::STATUS_TTL );
 		}
 	}

includes/core/class-article-worker.php

@@ -138,6 +138,7 @@ class PRAutoBlogger_Article_Worker {
 		$current       = get_transient( $transient_key );
 		if ( is_array( $current ) && 'running' === ( $current['status'] ?? '' ) ) {
 			$current['stage']        = $stage;
+			$current['last_updated'] = time();
 			set_transient( $transient_key, $current, 600 );
 		}
 	}

includes/core/class-pipeline-runner.php

@@ -216,6 +216,7 @@ class PRAutoBlogger_Pipeline_Runner {
 			'status'       => 'running',
 			'stage'        => sprintf( __( 'Generating article %1$d of %2$d…', 'prautoblogger' ), $done + 1, $total ),
 			'started'      => is_array( $current ) ? ( $current['started'] ?? time() ) : time(),
+			'last_updated' => time(),
 		], 600 );
 	}
 
@@ -257,6 +258,7 @@ class PRAutoBlogger_Pipeline_Runner {
 		$current = get_transient( $key );
 		if ( is_array( $current ) && 'running' === ( $current['status'] ?? '' ) ) {
 			$current['stage']        = $stage;
+			$current['last_updated'] = time();
 			set_transient( $key, $current, 600 );
 		}
 	}