feat: mobile response viewer — read full Claude responses via native scroll

Claude Code's Ink framework uses alternate screen buffer + VPA cursor
positioning, resulting in near-zero xterm.js scrollback on mobile.
Instead of fighting terminal scrollback, this adds a native scrollable
overlay that reads structured responses from Claude's JSONL transcripts.

- New API: GET /api/sessions/:id/last-response reads transcript JSONL
  - ?context=full returns full conversation thread (user + assistant)
  - Fallback to terminal buffer with ANSI stripping if no transcript
- Response viewer panel: bottom sheet with native iOS/Android scroll
- "More" button loads full conversation context as threaded view
- Eye icon in header bar (mobile only), no toolbar space impact

src/web/public/mobile.css

@@ -1195,6 +1195,20 @@ html.mobile-init .file-browser-panel {
     touch-action: none;
   }
 
+  /* Response viewer — show eye icon in header on mobile */
+  .btn-response-viewer-header {
+    display: inline-flex !important;
+  }
+
+  .response-viewer {
+    padding-bottom: var(--safe-area-bottom, 0px);
+  }
+
+  .response-viewer-body {
+    font-size: 12px;
+    padding: 12px;
+  }
+
   /* Compact welcome overlay for mobile */
   .welcome-content {
     max-width: calc(100vw - 1.5rem);