* fix(terminal): forward Windows Ctrl Alt chords
* fix(terminal): route rescued Windows Ctrl+Alt chords through xterm's own key encoders
Replace the hand-rolled Alt-prefix encoder in the custom key handler with a
narrow repair of xterm's third-level-shift classification. xterm's keyboard
service already computes the correct bytes for every input protocol (legacy
ESC-prefixed, kitty CSI-u, win32-input-mode) before _isThirdLevelShift
discards them on Windows Ctrl+Alt; rescuing only provably-genuine chords
(Chromium's layout-wide AltGraph simulation, crbug 762557) lets those
encoders deliver protocol-correct, layout-aware bytes with no duplicated
encoding knowledge in Orca.
Fixes vs the previous approach: kitty-mode TUIs now receive CSI-u instead of
legacy bytes, digits/punctuation no longer alias to plain Alt chords,
letters follow the logical layout (Dvorak/Colemak), Ctrl+Alt+Shift and
Ctrl+Alt+F-keys gain Linux parity, and handled keys get xterm's stock
preventDefault/stopPropagation. Firefox web clients keep stock behavior; a
real-Terminal contract test fails loudly if an xterm upgrade removes the
seam, degrading at runtime to the historical dropped-chord behavior.
Co-authored-by: Orca <help@stably.ai>
* Refactor Windows Ctrl+Alt chord test helpers and clarify AltGraph commen
- Extract a shared getCore() helper in the test file to dedupe repeated
`_core` casts across third-level-shift and keyboard-service lookups.
- Correct the AltGraph comment: Chromium simulates AltGraph per composing
keypress, not for the whole Ctrl+Alt press duration.
- Warn via console when xterm no longer exposes `_core._isThirdLevelShift`,
so a silent classification-repair failure is diagnosable in the wild.
* Clarify comment explaining why Windows Ctrl+Alt chords bypass AltGraph c
The comment previously implied Chromium always sets AltGraph=true for
composable chords; the revised wording states the actual mechanism
(Alt+Ctrl modifiers get replaced by AltGraph) so the inverse case is
unambiguous.
---------
Co-authored-by: Jinjing <6427696+AmethystLiang@users.noreply.github.com>
Co-authored-by: Orca <help@stably.ai>
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