improve AI rewrite UX and title quality

**AI button: dynamic tooltip hints**
- titleAiBtn and descAiBtn now show "Rewrite with AI" when the field
  already has user content, "Generate with AI" when empty.
- updateAiButtonHints() fires on every title/description input event
  and whenever syncStepFields() runs to keep hints current.

**Stronger rewrite prompt**
- When the user has typed a draft title or description, the prompt now
  shows it explicitly: "User's draft title (rewrite this): '...'"
- Rules changed from "improve its wording" to "Your only job is to
  polish its grammar and phrasing. Do NOT replace it with something
  different." — prevents the model from ignoring the user's text and
  generating fresh content from capture context.
- The suggested-title hint is suppressed when a draft title exists so
  the model doesn't silently swap the user's text for the auto-title.

**Title quality: generic window title filter**
- GENERIC_WINDOW_TITLES Set filters "New Tab", "Untitled", "Loading"
  etc. from the window-title path so they no longer produce titles
  like "Open New Tab in Chrome".

**Title quality: app name stripping for non-browser apps**
- stripBrowserNameSuffix now accepts an optional appName; it strips
  the app's display name and process name from the window title suffix
  using the same pattern as browser names.
- "Document1.docx - Word" with appName "winword" → "Document1.docx".
- buildCaptureTitle passes metadata.appName into the strip call.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

app/renderer/editor.js

@@ -227,6 +227,21 @@ class GuideEditor {
     return this.runAiGeneration('block', { blockId: block.id, button });
   }
 
+  updateAiButtonHints() {
+    const PLACEHOLDER_TITLES = new Set([
+      '', 'screen capture', 'window capture', 'region capture', 'capture',
+    ]);
+    if (this.dom.titleAiBtn) {
+      const val = (this.dom.titleInput?.value || '').trim();
+      const hasDraft = Boolean(val) && !PLACEHOLDER_TITLES.has(val.toLowerCase());
+      this.dom.titleAiBtn.title = hasDraft ? 'Rewrite step title with AI' : 'Generate step title with AI';
+    }
+    if (this.dom.descAiBtn) {
+      const hasDesc = Boolean((this.dom.descEditor?.innerText || '').trim());
+      this.dom.descAiBtn.title = hasDesc ? 'Rewrite description with AI' : 'Generate description with AI';
+    }
+  }
+
   get currentStep() {
     return this.stepMap.get(this.selectedStepId) || null;
   }
@@ -504,6 +519,7 @@ class GuideEditor {
       this.saveStepDebounced();
       this.renderStepList();
       this.emitMeta();
+      this.updateAiButtonHints();
     });
     this.dom.titleAiBtn.addEventListener('click', () => this.generateTitleWithAi(this.dom.titleAiBtn));
 
@@ -575,6 +591,7 @@ class GuideEditor {
       this.saveStepDebounced();
       this.emitMeta();
       this.updateToolbarState();
+      this.updateAiButtonHints();
     });
     this.dom.descEditor.addEventListener('keyup', () => this.updateToolbarState());
     this.dom.descEditor.addEventListener('mouseup', () => this.updateToolbarState());
@@ -1019,6 +1036,7 @@ class GuideEditor {
     if (document.activeElement !== this.dom.titleInput) this.dom.titleInput.value = step.title || '';
     if (document.activeElement !== this.dom.descEditor) this.dom.descEditor.innerHTML = step.descriptionHtml || '';
     this.dom.statusSelect.value = step.status || 'todo';
+    this.updateAiButtonHints();
     this.dom.hiddenToggle.querySelector('input').checked = Boolean(step.hidden);
     this.dom.skippedToggle.querySelector('input').checked = Boolean(step.skipped);
     this.dom.forceNewPageToggle.querySelector('input').checked = Boolean(step.forceNewPage);