* fix(process): auto-detect PTY cursor key mode for send-keys
When a PTY session sends smkx (\x1b[?1h) or rmkx (\x1b[?1l) to switch
cursor key mode, send-keys now detects this and encodes cursor keys
accordingly.
- smkx/rmkx detection in handleStdout before sanitizeBinaryOutput
- cursorKeyMode stored in ProcessSession
- encodeKeySequence accepts cursorKeyMode parameter
- DECCKM_SS3_KEYS for application mode (arrows + home/end)
- CSI sequences for normal mode
- Modified keys (including alt) always use xterm modifier scheme
- Extract detectCursorKeyMode for unit testing
- Use lastIndexOf to find last toggle in chunk (later one wins)
Fixes#51488
* fix: fail loud when PTY cursor mode is unknown (#51490) (thanks @liuy)
* style: format process send-keys guard (#51490) (thanks @liuy)
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Co-authored-by: Ayaan Zaidi <hi@obviy.us>
