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/keybindings.ts

@@ -0,0 +1,145 @@
+import { matchesKey } from "./keys.js";
+
+/**
+ * Editor actions that can be bound to keys.
+ */
+export type EditorAction =
+	// Cursor movement
+	| "cursorUp"
+	| "cursorDown"
+	| "cursorLeft"
+	| "cursorRight"
+	| "cursorWordLeft"
+	| "cursorWordRight"
+	| "cursorLineStart"
+	| "cursorLineEnd"
+	// Deletion
+	| "deleteCharBackward"
+	| "deleteCharForward"
+	| "deleteWordBackward"
+	| "deleteToLineStart"
+	| "deleteToLineEnd"
+	// Text input
+	| "newLine"
+	| "submit"
+	| "tab"
+	// Selection/autocomplete
+	| "selectUp"
+	| "selectDown"
+	| "selectConfirm"
+	| "selectCancel"
+	// Clipboard
+	| "copy";
+
+/**
+ * Key identifier string (e.g., "ctrl+c", "shift+ctrl+p", "escape").
+ */
+export type KeyId = string;
+
+/**
+ * Editor keybindings configuration.
+ */
+export type EditorKeybindingsConfig = {
+	[K in EditorAction]?: KeyId | KeyId[];
+};
+
+/**
+ * Default editor keybindings.
+ */
+export const DEFAULT_EDITOR_KEYBINDINGS: Required<EditorKeybindingsConfig> = {
+	// Cursor movement
+	cursorUp: "up",
+	cursorDown: "down",
+	cursorLeft: "left",
+	cursorRight: "right",
+	cursorWordLeft: ["alt+left", "ctrl+left"],
+	cursorWordRight: ["alt+right", "ctrl+right"],
+	cursorLineStart: ["home", "ctrl+a"],
+	cursorLineEnd: ["end", "ctrl+e"],
+	// Deletion
+	deleteCharBackward: "backspace",
+	deleteCharForward: "delete",
+	deleteWordBackward: ["ctrl+w", "alt+backspace"],
+	deleteToLineStart: "ctrl+u",
+	deleteToLineEnd: "ctrl+k",
+	// Text input
+	newLine: ["shift+enter", "alt+enter"],
+	submit: "enter",
+	tab: "tab",
+	// Selection/autocomplete
+	selectUp: "up",
+	selectDown: "down",
+	selectConfirm: "enter",
+	selectCancel: "escape",
+	// Clipboard
+	copy: "ctrl+c",
+};
+
+/**
+ * Manages keybindings for the editor.
+ */
+export class EditorKeybindingsManager {
+	private actionToKeys: Map<EditorAction, KeyId[]>;
+
+	constructor(config: EditorKeybindingsConfig = {}) {
+		this.actionToKeys = new Map();
+		this.buildMaps(config);
+	}
+
+	private buildMaps(config: EditorKeybindingsConfig): void {
+		this.actionToKeys.clear();
+
+		// Start with defaults
+		for (const [action, keys] of Object.entries(DEFAULT_EDITOR_KEYBINDINGS)) {
+			const keyArray = Array.isArray(keys) ? keys : [keys];
+			this.actionToKeys.set(action as EditorAction, [...keyArray]);
+		}
+
+		// Override with user config
+		for (const [action, keys] of Object.entries(config)) {
+			if (keys === undefined) continue;
+			const keyArray = Array.isArray(keys) ? keys : [keys];
+			this.actionToKeys.set(action as EditorAction, keyArray);
+		}
+	}
+
+	/**
+	 * Check if input matches a specific action.
+	 */
+	matches(data: string, action: EditorAction): boolean {
+		const keys = this.actionToKeys.get(action);
+		if (!keys) return false;
+		for (const key of keys) {
+			if (matchesKey(data, key)) return true;
+		}
+		return false;
+	}
+
+	/**
+	 * Get keys bound to an action.
+	 */
+	getKeys(action: EditorAction): KeyId[] {
+		return this.actionToKeys.get(action) ?? [];
+	}
+
+	/**
+	 * Update configuration.
+	 */
+	setConfig(config: EditorKeybindingsConfig): void {
+		this.buildMaps(config);
+	}
+}
+
+// Global instance
+let globalEditorKeybindings: EditorKeybindingsManager | null = null;
+
+export function getEditorKeybindings(): EditorKeybindingsManager {
+	if (!globalEditorKeybindings) {
+		globalEditorKeybindings = new EditorKeybindingsManager();
+	}
+	return globalEditorKeybindings;
+}
+
+export function setEditorKeybindings(manager: EditorKeybindingsManager): void {
+	globalEditorKeybindings = manager;
+}