No behavior change. Prepares the split pane's second terminal (and later
grid tiles) to share what today only the primary terminal has:
- _inputSocketFor/_registerInputSocket/_unregisterInputSocket: the
exactly-once input queue, its ACK handling and the redelivery sweep now
deliver over any registered socket bound to a session, not only
this._ws. ACKs are routed by the receiving socket's session; silence is
judged per socket; a stale handle cannot unregister its replacement.
- registerFilePathLinkProvider, cleanedTerminalSelection,
copyTerminalSelection and _handleImagePaste take an optional target
terminal and session (defaults: the primary pane).
- _focusedPane() is the one place to ask which pane the keyboard is in
(primary only, for now); _forEachTile() replaces the _splitPane special
cases in the font, family, weight, skin and resize paths.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
