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/terminal-font-weight.test.ts

@@ -74,6 +74,18 @@ function makeApp(opts: { teammates?: number; terminal?: ReturnType<typeof fakeTe
   }
   const app = {
     applyTerminalFontWeights: mixin.applyTerminalFontWeights,
+    // The REAL geometry chain, not stubs. A font change moves the cell size, so
+    // it moves cols/rows, and `applyTerminalFontWeights` now routes its refit
+    // through the one function that floors the result and reports it (#464).
+    // Wiring the real methods keeps `fit` an assertion about what the terminal
+    // actually did rather than about which helper happened to be called.
+    _refitAfterCellSizeChange: mixin._refitAfterCellSizeChange,
+    syncTerminalGeometry: mixin.syncTerminalGeometry,
+    _resizeTerminalTo: mixin._resizeTerminalTo,
+    getTerminalDimensions: mixin.getTerminalDimensions,
+    // No session: `_refitAfterCellSizeChange` then refits locally and sends
+    // nothing, which is what these cases are about.
+    activeSessionId: null,
     _awaitTerminalFont: vi.fn(() => Promise.resolve()),
     terminal: opts.terminal === undefined ? fakeTerminal() : opts.terminal,
     fitAddon: { fit },