fix(tui): distinguish LF from Return in key parser

[zengzheqing]

Summary

Fix Hermes TUI handling of raw LF input from terminals such as Ghostty.

Ghostty users can configure Shift+Enter / Ctrl+Enter as:

keybind = shift+enter=text:\n
keybind = ctrl+enter=text:\n

Codex and Hermes classic CLI treat raw LF (\n) as newline intent. Hermes TUI previously collapsed raw LF into ordinary Return semantics, causing Shift+Enter to submit instead of inserting a newline.

This change preserves the distinction:

• raw LF (\n) maps to Ctrl+Return / newline intent
• raw CR (\r) maps to ordinary Return / submit intent

Test Plan

• npm test -- packages/hermes-ink/src/ink/events/cmd-shortcuts.test.ts
• npm run type-check
• npm run build

[alt-glitch]

This PR appears to duplicate #18229 which also fixes the LF/CR distinction in parse-keypress.ts for Shift+Enter (fixes #18228). The approach is slightly different (this one sets key.ctrl = true for LF rather than preserving key.raw), but both target the same root cause.