fix(FN-1043): fix terminal mobile keyboard layout

- Defer fitAddon.fit() via requestAnimationFrame after CSS repaint to ensure container dimensions are settled
- Add overflow:hidden to keyboard-open CSS rule to prevent layout shift
- Add regression tests for xterm re-fit on mobile keyboard open/close
- Update terminal mobile keyboard documentation in README files

packages/dashboard/README.md

@@ -126,7 +126,7 @@ Access a fully functional PTY (pseudo-terminal) shell directly from the dashboar
 - **Scrollback Buffer**: 5KB of scrollback history with replay on reconnect
 - **Reconnection Support**: Automatic reconnect with exponential backoff if connection drops
 - **Reliable Prompt Delivery**: Initial shell prompt visible through first keyst press
-- **Mobile Keyboard Support**: On mobile devices, the terminal modal automatically adjusts when the on-screen keyboard opens, constraining its height to fit entirely above the keyboard. This ensures the status bar and terminal content remain visible and interactive without bottom overlap. Protected by regression tests for both CSS contract and component behavior.
+- **Mobile Keyboard Support**: On mobile devices, the terminal modal automatically adjusts when the on-screen keyboard opens, constraining its height to fit entirely above the keyboard. The xterm.js terminal view re-fits its rows/columns after the modal shrinks (deferred via `requestAnimationFrame` to ensure CSS variable changes are committed before measuring). This ensures the status bar and terminal content remain visible and interactive without bottom overlap. Protected by regression tests for both CSS contract and component behavior.
 - **Keyboard Shortcuts**:
   - `Ctrl+C` - Send SIGINT to process (copy if text selected)
   - `Ctrl+V` - Paste from clipboard