feat: configurable keybindings for all editor and app actions

All keybindings configurable via ~/.pi/agent/keybindings.json

Editor actions:
- cursorUp, cursorDown, cursorLeft, cursorRight
- cursorWordLeft, cursorWordRight, cursorLineStart, cursorLineEnd
- deleteCharBackward, deleteCharForward, deleteWordBackward
- deleteToLineStart, deleteToLineEnd
- newLine, submit, tab
- selectUp, selectDown, selectConfirm, selectCancel

App actions:
- interrupt, clear, exit, suspend
- cycleThinkingLevel, cycleModelForward, cycleModelBackward
- selectModel, expandTools, toggleThinking, externalEditor

Also adds support for numpad Enter key (Kitty protocol codepoint 57414
and SS3 M sequence)

Example emacs-style keybindings.json:
{
  "cursorUp": ["up", "ctrl+p"],
  "cursorDown": ["down", "ctrl+n"],
  "cursorLeft": ["left", "ctrl+b"],
  "cursorRight": ["right", "ctrl+f"],
  "deleteCharForward": ["delete", "ctrl+d"],
  "cycleModelForward": "ctrl+o"
}

packages/tui/src/index.ts

@@ -20,45 +20,18 @@ export { type SettingItem, SettingsList, type SettingsListTheme } from "./compon
 export { Spacer } from "./components/spacer.js";
 export { Text } from "./components/text.js";
 export { TruncatedText } from "./components/truncated-text.js";
-// Kitty keyboard protocol helpers
+// Keybindings
 export {
-	isAltBackspace,
-	isAltEnter,
-	isAltLeft,
-	isAltRight,
-	isArrowDown,
-	isArrowLeft,
-	isArrowRight,
-	isArrowUp,
-	isBackspace,
-	isCtrlA,
-	isCtrlC,
-	isCtrlD,
-	isCtrlE,
-	isCtrlG,
-	isCtrlK,
-	isCtrlL,
-	isCtrlLeft,
-	isCtrlO,
-	isCtrlP,
-	isCtrlRight,
-	isCtrlT,
-	isCtrlU,
-	isCtrlW,
-	isCtrlZ,
-	isDelete,
-	isEnd,
-	isEnter,
-	isEscape,
-	isHome,
-	isShiftCtrlD,
-	isShiftCtrlO,
-	isShiftCtrlP,
-	isShiftEnter,
-	isShiftTab,
-	isTab,
-	Keys,
-} from "./keys.js";
+	DEFAULT_EDITOR_KEYBINDINGS,
+	type EditorAction,
+	type EditorKeybindingsConfig,
+	EditorKeybindingsManager,
+	getEditorKeybindings,
+	type KeyId,
+	setEditorKeybindings,
+} from "./keybindings.js";
+// Keyboard input handling
+export { matchesKey, parseKey } from "./keys.js";
 // Terminal interface and implementations
 export { ProcessTerminal, type Terminal } from "./terminal.js";
 // Terminal image support