fix(terminal): forward touch scrolls to the CLI transcript on mobile

Touch drags and flick momentum on forwarding-capable sessions (codex,
claude >= 2.1.187) now go to the CLI as coalesced SGR wheel reports via
the shared _forwardScrollToApp helper, exactly like the desktop wheel:
snap the viewport home first, then encode. Before this, every phone or
tablet swipe scrolled the local buffer of stale repaint frames and
dragged the CLI's pinned input box off the screen (the mobile half of
issue #205). The _shouldForwardWheelToApp gate is shared, so the
local-scrollback opt-out setting and the CLI version gate apply to touch
exactly as they do to the wheel; shell and other local modes keep the
existing local touch scrolling and the scroll-to-top history re-pull.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/terminal-touch-tap.test.ts

@@ -462,6 +462,39 @@ describe('terminal touch tap mouse guard', () => {
     expect(sent).toHaveLength(1);
   });
 
+  it('forwarded scrolls (wheel AND touch) snap the viewport home first, then encode SGR ticks', () => {
+    const { app } = loadTerminalUiHarness();
+    const sent: Array<{ id: string; data: string }> = [];
+    app.activeSessionId = 'sess-1';
+    app.sessions = new Map([['sess-1', { mode: 'claude' }]]);
+    app._sendInputEphemeral = (id: string, data: string) => sent.push({ id, data });
+    const scrolledToBottom: boolean[] = [];
+    app.terminal = {
+      cols: 80,
+      rows: 24,
+      // Scrolled up into local scrollback: SGR coordinates address the LIVE
+      // screen, so the report would hit-test the wrong row without the snap.
+      buffer: { active: { viewportY: 10, baseY: 50 } },
+      scrollToBottom: () => scrolledToBottom.push(true),
+      element: {
+        querySelector: () => ({ getBoundingClientRect: () => ({ left: 0, top: 0 }) }),
+      },
+      _core: { _renderService: { dimensions: { css: { cell: { width: 8, height: 16 } } } } },
+    };
+
+    app._forwardScrollToApp(50, 50, -3);
+    expect(scrolledToBottom).toEqual([true]);
+    app._flushWheelSgrQueue();
+    expect(sent).toEqual([{ id: 'sess-1', data: '\x1b[<64;7;4M'.repeat(3) }]);
+
+    // Already at the bottom: no snap, just the report.
+    app.terminal.buffer.active.viewportY = 50;
+    app._forwardScrollToApp(50, 50, 2);
+    expect(scrolledToBottom).toHaveLength(1);
+    app._flushWheelSgrQueue();
+    expect(sent).toHaveLength(2);
+  });
+
   it('allows trusted mouse events after the tap window expires', () => {
     const { app, setNow } = loadTerminalUiHarness();
     const { element, dispatch } = createElementHarness();