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>

docs/wiki/The-Dashboard.md

@@ -219,7 +219,8 @@ Worth knowing:
   `~/.claude/settings.json`), so the wheel scrolls the conversation rather than the terminal.
   Claude's default inline view keeps its history in the terminal and scrolls locally. `Shift+Wheel` is
   always local scrollback. OpenCode's wheel and swipes page its own conversation
-  (PageUp/PageDown). Other CLIs scroll locally.
+  (PageUp/PageDown); in a grid tile or the split view's second pane the wheel does
+  too. Other CLIs scroll locally.
 - **Selection copy.** `Ctrl+C` copies when text is selected and interrupts when it is not.
   `Ctrl+Shift+C` always copies.
 - **Selecting where the CLI owns the mouse.** `Shift+drag` starts a selection even in a pane