feat: optional terminal mouse taps, off by default

[dorokuma]

After the soft-keyboard fix for mouse-aware TUIs, tapping the terminal always opens the keyboard even when mouse tracking is on. That is what we want, but the tap is still forwarded as a mouse report (SGR, e.g. 0;col;rowM / 0;col;rowm).

When the remote side is a plain shell, or mouse tracking was left on after a TUI exited, those reports show up as garbage on the command line. Coordinates change with every tap, so it looks random.

Approach

Keep the always-show-keyboard behavior. Make sending mouse taps optional.

• New Appearance → Terminal toggle: Send mouse taps
• Subtitle: Forward terminal taps as mouse clicks when apps enable mouse tracking.
• Default off so taps only focus the terminal / open the keyboard and do not inject mouse sequences
• When on, same as today: taps are reported to mouse-aware apps (vim, htop, Bubble Tea, etc.)

Persisted with the other appearance prefs, included in backup/restore. Uses conduit_vt's existing PointerInputs / TerminalController.setPointerInputs so we only gate tap reporting; keyboard focus callbacks are unchanged.

Changes

• lib/core/theme/theme_preferences_repository.dart — store terminalMouseInput (default false)
• lib/core/theme/theme_controller.dart — load/save/toggle
• lib/core/presentation/theme_sheet.dart — Appearance UI
• lib/features/terminal/presentation/widgets/terminal_surface.dart — wire pointer inputs
• lib/features/terminal/presentation/terminal_page.dart — pass preference into the surface
• lib/features/backup/data/app_backup_service.dart — backup field
• tests for default/persist and the Appearance toggle

Testing

• Unit: theme prefs default off / persist on; Appearance sheet toggle; terminal surface still builds with the new flag
• Device: with the toggle off, blank taps open the keyboard and no mouse garbage; with it on, mouse-aware TUI clicks work again

[gwitko]

Thanks!