fix: rotate activity text when tool stream preview goes stale

When a tool (e.g. Write) streams slowly, the "receiving N bytes..."
preview would freeze. After 2s of no updates, rotate through
"Working...", "Writing...", "Processing..." every 3s so the user
sees the operation is still in progress. Timers are cleaned up
when tool info arrives.

Author: abose

src/core-ai/AIChatPanel.js

@@ -48,6 +48,8 @@ define(function (require, exports, module) {
     // --- AI event trace logging (compact, non-flooding) ---
     let _traceTextChunks = 0;
     let _traceToolStreamCounts = {}; // toolId → count
+    let _toolStreamStaleTimer = null;    // timer to start rotating activity text
+    let _toolStreamRotateTimer = null;   // interval for cycling activity phrases
 
     // DOM references
     let $panel, $messages, $status, $statusText, $textarea, $sendBtn, $stopBtn;
@@ -420,6 +422,32 @@ define(function (require, exports, module) {
             $tool.find(".ai-tool-preview").text(preview);
             _scrollToBottom();
         }
+
+        // Reset staleness timer — if no new stream event arrives within 2s,
+        // rotate through activity phrases so the user sees something is happening.
+        clearTimeout(_toolStreamStaleTimer);
+        clearInterval(_toolStreamRotateTimer);
+        _toolStreamStaleTimer = setTimeout(function () {
+            const phrases = [
+                Strings.AI_CHAT_WORKING,
+                Strings.AI_CHAT_WRITING,
+                Strings.AI_CHAT_PROCESSING
+            ];
+            let idx = 0;
+            const $livePreview = $tool.find(".ai-tool-preview");
+            if ($livePreview.length && !$tool.hasClass("ai-tool-done")) {
+                $livePreview.text(phrases[idx]);
+            }
+            _toolStreamRotateTimer = setInterval(function () {
+                idx = (idx + 1) % phrases.length;
+                const $p = $tool.find(".ai-tool-preview");
+                if ($p.length && !$tool.hasClass("ai-tool-done")) {
+                    $p.text(phrases[idx]);
+                } else {
+                    clearInterval(_toolStreamRotateTimer);
+                }
+            }, 3000);
+        }, 2000);
     }
 
     /**
@@ -925,6 +953,10 @@ define(function (require, exports, module) {
             }).css("cursor", "pointer").addClass("ai-tool-label-clickable");
         }
 
+        // Clear any stale-preview timers now that tool info arrived
+        clearTimeout(_toolStreamStaleTimer);
+        clearInterval(_toolStreamRotateTimer);
+
         // Delay marking as done so the streaming preview stays visible briefly.
         // The ai-tool-done class hides the preview via CSS; deferring it lets the
         // browser paint the preview before it disappears.

src/nls/root/strings.js

@@ -1844,6 +1844,9 @@ define({
     "AI_CHAT_LABEL_CLAUDE": "Claude",
     "AI_CHAT_SEND_ERROR": "Failed to send message: {0}",
     "AI_CHAT_EDIT_NOT_FOUND": "Text not found in file \u2014 it may have changed",
+    "AI_CHAT_WORKING": "Working...",
+    "AI_CHAT_WRITING": "Writing...",
+    "AI_CHAT_PROCESSING": "Processing...",
 
     // demo start - Phoenix Code Playground - Interactive Onboarding
     "DEMO_SECTION1_TITLE": "Edit in Live Preview",