fix(tiles): send a tile's click report ephemeral, review follow-up

The tile's hand-encoded click report went through _handleDesktopTerminalClick
and _sendSyntheticSgrTap to _sendInputAsync, so it took a seq, was persisted
and would be redelivered after a reload. The documented TerminalTile rule
(CLAUDE.md, Split-pane sessions) is that only typed input enters that queue
and focus/mouse reports go out ephemeral, and the tile's own _onTerminalData
says the same. Before #555 an opencode tile's click went through xterm's
encoder and that ephemeral path. A click still unacknowledged when the page
reloads, or sent during a server restart, could be replayed onto a later
screen, where a press+release can pick a dialog option.

_sendSyntheticSgrTap now takes an opt-in `ephemeral` field on its target and
sends through _sendInputEphemeral when it is set; _handleDesktopTerminalClick
passes the target through unchanged, and TerminalTile._installClickListener
sets it. Without the flag nothing changes, so the primary pane's own click
and touch tap reports stay on _sendInputAsync exactly as before (whether the
primary pane should also go ephemeral is a separate question, out of scope
here).

Tests: the tile case now requires a frame with no seq and nothing pending in
the reliable queue, and the targeted-click case in terminal-touch-tap spies on
both send paths: a target with the flag goes ephemeral, an untargeted click
and an untargeted tap stay durable. Dropping `ephemeral: true` from the tile,
or the branch in _sendSyntheticSgrTap, turns the matching test red.

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

test/terminal-tile-scroll.test.ts

@@ -514,13 +514,16 @@ describe('a tile reports a plain click to a CLI with mouse tracking on', () => {
   });
   const TAP = '\x1b[<0;21;6M\x1b[<0;21;6m';
 
-  it("sends one seq-tagged SGR press+release on the tile's socket, from the tile's own geometry", async () => {
+  it("sends one ephemeral SGR press+release on the tile's socket, from the tile's own geometry", async () => {
     const app = makeApp({ other: { mode: 'shell' }, 's-tile': { mode: 'opencode', cliMouseTracking: true } });
     const { ws, mount } = await connectTile(app);
 
     mount.fire('click', click());
 
-    expect(ws.inputFrames().map((f) => [f.d, typeof f.seq])).toEqual([[TAP, 'number']]);
+    // No seq: like every mouse report from a tile, it never enters the
+    // persisted exactly-once queue, so a reload cannot replay it.
+    expect(ws.inputFrames().map((f) => [f.d, typeof f.seq])).toEqual([[TAP, 'undefined']]);
+    expect((app._pendingDeliveries as Map<string, unknown[]>).get('s-tile')?.length ?? 0).toBe(0);
   });
 
   it('sends nothing without the flag, over a selection, over its own hovered link, or scrolled up', async () => {