test(terminal): follow the existing suites to the one geometry owner

The gate caught fourteen failures the focused tests could not: every harness
that builds a partial app out of cherry-picked mixin methods, and every source
guard that named `fitAddon.fit()` by hand.

Most are wiring — `syncTerminalGeometry`, `_refitAfterCellSizeChange` and
`_resizeTerminalTo` added to the fakes so the real chain runs rather than a
stub of it. `file-browser-search` is the one that shows why it matters: without
the method on the fake, selectSession's unconditional call threw into its own
catch and every later assertion in the file measured a load that never
happened.

Two are not wiring.

`detached-session-pane-sizing` pinned the behaviour this change deliberately
reverses. It asserted the LOCAL fit still runs for a session owned by its own
window — "withhold the send, never the reflow" — so the assertion is restated
rather than patched, with the reason beside it and in the file's docblock: a
reflow the PTY is never told about leaves this xterm rendering a CLI's frames
against a shape that does not exist, and the popup that owns the pane is
drawing for its own width regardless. The old rule bought a garbled frame, not
a correct one.

`mobile-prompt-composer` sliced `_cleanupSessionData` as a fixed 1200-character
window, so the assertion depended on how much unrelated code sat above the line
it cared about. It reads the whole method now.

`terminal-scroll-intent` records `syncTerminalGeometry` rather than `fit`,
under its own name: recording a bare fit there would name the very thing the
subject was changed to stop doing.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/file-browser-search.test.ts

@@ -292,6 +292,10 @@ function loadRealSelectSessionHarness(options: { terminalFailure?: boolean } = {
   app._beginBufferLoad = vi.fn(() => 1);
   app._isLoadingBuffer = false;
   app.fitAddon = { fit: vi.fn() };
+  // selectSession fits through the one owner now, which also applies the floor
+  // it reports to the PTY (#464). Without it on the fake, the unconditional
+  // call throws into selectSession's catch and nothing after it runs.
+  app.syncTerminalGeometry = vi.fn(() => ({ cols: 120, rows: 40 }));
   app.sendResize = vi.fn(() => {
     resizeCalls++;
     return resizeCalls === 1 ? terminalBoundary.promise : Promise.resolve(false);