test(tiles): the load-queue test drives TerminalTile on the shared fakes

tile-grid-load-queue carried its own FakeSocket, FakeFit and FakeTerminal,
near-copies of terminal-tile-input's. It now imports
test/mocks/terminal-tile-fakes.ts, which gains what only it used:
FakeSocket.drop(code), the terminal's scrollToLine / scrollToTop, and the
replay-pace extension (an opt-in `holdParse` that keeps write callbacks
from running, as on a disposed xterm, and empty writes left out of
`writes`, since the replay queues one only to hear it was parsed).

One definition serves both files with no per-file switch:
terminal-tile-input passes unchanged with the extension in place, the
shared fit resizes to the default 80x24 the tile already has, and
FakeSocket.OPEN is the real value. Every assertion is unchanged.
Mutation-checked through the shared fakes: dropping destroy()'s replay
settle fails the destroy-while-parsing case, a queue that runs two loads
at once fails eleven cases, and a tile that never registers its input
socket fails six in terminal-tile-input.

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

test/mocks/terminal-tile-fakes.ts

@@ -37,6 +37,11 @@ export class FakeSocket {
   inputFrames() {
     return this.sent.filter((f) => f.t === 'i');
   }
+  /** The connection drops: closed, and the tile hears `code`. */
+  drop(code = 1006) {
+    this.readyState = 3;
+    this.onclose?.({ code });
+  }
 }
 
 /** The fit addon: proposes `FakeFit.proposed` and, like the real one, resizes to it (NaN = hidden pane). */
@@ -90,9 +95,13 @@ export class FakeTerminal {
   }
   registerLinkProvider() {}
   writes: string[] = [];
+  /** Set by a test: write callbacks never run, as on a disposed xterm. */
+  holdParse = false;
   write(data: string, cb?: () => void) {
-    this.writes.push(data);
-    cb?.();
+    // An empty write puts nothing on screen; the replay queues one only to hear
+    // (its callback) that everything before it has been parsed.
+    if (data) this.writes.push(data);
+    if (!this.holdParse) cb?.();
   }
   clear() {
     this.writes.push('<CLEAR>');
@@ -103,6 +112,8 @@ export class FakeTerminal {
     this.cols = cols;
     this.rows = rows;
   }
+  scrollToLine() {}
+  scrollToTop() {}
   dispose() {}
   type(data: string) {
     this.dataCb?.(data);