feat(macos): auto-select newline mode for terminal apps

[H-Chris233]

Summary

• Adds a Line Feed option that sends U+000A / Ctrl+J for terminal CLI agents.
• Adds Auto as the new macOS newline default.
• Auto uses Line Feed in known terminal apps and Shift+Return elsewhere.
• Resolves the target once from the app captured at dictation start, so switching between apps does not require changing settings.
• Keeps Shift+Return, Line Feed, and Return as explicit overrides.

Detection

Auto reuses the existing case-insensitive terminal bundle ID prefix list used by the host-document safety gate. This covers Terminal, iTerm2, Warp, WezTerm, Alacritty, kitty, Hyper, Tabby, and Ghostty. Unknown apps fall back to Shift+Return.

Validation

• cargo test --manifest-path openless-all/app/src-tauri/Cargo.toml macos_ --lib (14 passed)
• cargo test --manifest-path openless-all/app/src-tauri/Cargo.toml --lib (1254 passed, 7 ignored)
• npm test (56 frontend tests passed)
• npm run build
• git diff --check

Validation was run locally on Windows. The macOS event behavior still needs macOS CI and/or real-device confirmation.

Closes #982