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/coding-agent/src/modes/interactive/components/hook-editor.ts

@@ -7,7 +7,7 @@ import { spawnSync } from "node:child_process";
 import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
-import { Container, Editor, isCtrlC, isCtrlG, isEscape, Spacer, Text, type TUI } from "@mariozechner/pi-tui";
+import { Container, Editor, matchesKey, Spacer, Text, type TUI } from "@mariozechner/pi-tui";
 import { getEditorTheme, theme } from "../theme/theme.js";
 import { DynamicBorder } from "./dynamic-border.js";
 
@@ -68,13 +68,13 @@ export class HookEditorComponent extends Container {
 		}
 
 		// Escape or Ctrl+C to cancel
-		if (isEscape(keyData) || isCtrlC(keyData)) {
+		if (matchesKey(keyData, "escape") || matchesKey(keyData, "ctrl+c")) {
 			this.onCancelCallback();
 			return;
 		}
 
 		// Ctrl+G for external editor
-		if (isCtrlG(keyData)) {
+		if (matchesKey(keyData, "ctrl+g")) {
 			this.openExternalEditor();
 			return;
 		}