fix(tiles): page a hollow tile's CLI transcript and report its clicks (#555 parity)

#555 made the primary pane page opencode's transcript with PageUp/PageDown
from the wheel, because opencode draws in place on the alternate screen and
leaves the browser's buffer with no scrollback. A TerminalTile (a grid tile,
the split's Pane B) left every wheel to xterm, so in an opencode tile the
wheel scrolled nothing, or only stale rows.

The tile now runs the primary pane's own gates aimed at itself (its terminal,
its session, never the active one): xterm's tracking mode, the Claude
forwarding gate, then the hollow-buffer test. A wheel that passes them is
consumed in the capture phase and turned into PageUp/PageDown through the
shared pageKeysForTravel math, coalesced per tile (40 ms, 512 bytes, the twin
of the primary pane's queue) and sent ephemeral on the tile's own socket.
Every other wheel stays with xterm as before, the shell history pull
included. The file names no CLI: the mode rules stay in terminal-ui.js, and
terminal-tile.js joins the frontend no-id-branching guard.

A plain port of the primary's baseY === 0 test would almost never fire in a
grid. A tile's first capture is taken at the PTY's previous size (usually the
taller primary pane's) and written into a shorter xterm, and its own
row-shrinking fits (zoom-out, divider drags, tile count changes) push more
rows above the screen. The tile counts those rows as its own overflow: all of
them after a load whose capture held a single screen (the server's
captureRows), plus whatever a local fit or a PTY geometry report pushes up,
reset by a clear and clamped to baseY. The paging gate gets baseY minus that
count. Output that scrolls real lines still counts as history, so the tile
stops paging there.

#555's other half, stripping opencode's mouse DECSETs so a drag selects text,
is server-side and already reached tile sockets. It also left the tile's
xterm unable to encode opencode's clicks, so the tile now installs the
primary pane's desktop click report (bubble phase, gated on the session's
cliMouseTracking, the tile's own link hover and selection). Both listeners,
the flush timer and the page-key state are torn down in destroy().

Still out of scope, as the fileoverview now says: touch paging (tiles have
no touch path) and SGR wheel forwarding to Claude's fullscreen renderer
(tile-grid-plan follow-up 4), so a fullscreen Claude tile keeps leaving the
wheel to xterm.

Tests: test/terminal-tile-scroll.test.ts drives a real tile in the vm
harness (session targeting, every no-page case, accumulation, the cap,
coalescing, byte parity with the primary pane, the overflow discount through
a load, a fit, a geometry report and a clear, the click report and destroy);
the discount cases fail with it removed. The fake xterm gains opt-in row
emulation. test/terminal-tile-scroll.browser.test.ts checks the same model
against a real xterm with trusted wheel events (browser suite, not the gate).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/frontend-cli-no-id-branching.test.ts

@@ -3,7 +3,9 @@
  * (`session-ui.js`, `mobile-overview.js`), plus the files that draw a session
  * header's harness logo and model (`constants.js`, `terminal-split.js`,
  * `tile-grid.js`: the logo's `run-mode-dot <cliId>` class is the id as DATA),
- * mirroring
+ * and `terminal-tile.js`, whose wheel paging and click reports reach the
+ * primary pane's CLI rules through terminal-ui.js and must not grow a copy of
+ * them, mirroring
  * `test/cli-registry-no-id-branching.test.ts` for the backend registry.
  *
  * Deliberately scoped to ONLY these two files, not all of `src/web/public/`.
@@ -24,7 +26,14 @@ import { fileURLToPath } from 'node:url';
 import { STOCK_CLIS } from '../src/config/cli-registry/stock.js';
 
 const PUBLIC = fileURLToPath(new URL('../src/web/public/', import.meta.url));
-const SCANNED_FILES = ['session-ui.js', 'mobile-overview.js', 'constants.js', 'terminal-split.js', 'tile-grid.js'];
+const SCANNED_FILES = [
+  'session-ui.js',
+  'mobile-overview.js',
+  'constants.js',
+  'terminal-split.js',
+  'tile-grid.js',
+  'terminal-tile.js',
+];
 
 /**
  * Every currently-surviving branch, each with the COUNT of physical call
@@ -100,6 +109,20 @@ const ALLOWED_BRANCHES: Record<string, { count: number; reason: string }> = {
     reason: 'attach route: a shell session attaches through /shell, an agent through /interactive',
   },
 
+  // terminal-tile.js: the pane's two shell-only mechanisms, both mirrors of the
+  // primary pane's own shell checks (terminal-ui.js / app.js). Its wheel
+  // paging and click reports name no CLI: they ask terminal-ui.js's gates.
+  "terminal-tile.js::mode !== 'shell'": {
+    count: 2,
+    reason:
+      'Ctrl+Z reaches the PTY only in a shell (job control), and the scroll-to-top history pull is shell-only, ' +
+      'both as in the primary pane',
+  },
+  "terminal-tile.js::mode === 'shell'": {
+    count: 1,
+    reason: 'the load query: a shell loads the bounded tail= window instead of a full capture, as in the primary pane',
+  },
+
   // mobile-overview.js: shell is exempt from the isCliAvailable() gate the
   // same way the toolbar's #runModeMenu exempts it (shell needs no CLI).
   "mobile-overview.js::mode !== 'shell'": {
@@ -188,7 +211,7 @@ function actualCounts(): Map<string, number> {
 }
 
 describe('no NEW CLI-id branching in the scanned frontend files', () => {
-  it('scans both files (sanity)', () => {
+  it('scans every listed file (sanity)', () => {
     // If this drops to zero the scanner or the file list drifted and every
     // assertion below would pass vacuously.
     const scannedBytes = SCANNED_FILES.reduce((n, f) => n + readFileSync(PUBLIC + f, 'utf-8').length, 0);