feat: add keyboard command for raw keyboard input (#521)

Adds `keyboard type` and `keyboard insertText` subcommands that
operate on the currently focused element without requiring a selector.

Essential for contenteditable editors (Lexical, ProseMirror, CodeMirror,
Monaco) where `type <selector>` doesn't trigger the editor's internal
event pipeline (beforeinput/DOM mutation).

- `keyboard type <text>` — page.keyboard.type() with real keystrokes
- `keyboard insertText <text>` — page.keyboard.insertText()

Note: `keyboard press` intentionally omitted — the existing top-level
`press` command already operates on current focus.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/types.ts

@@ -667,10 +667,13 @@ export interface ErrorsCommand extends BaseCommand {
   clear?: boolean;
 }
 
-// Keyboard shortcuts
+// Raw keyboard input (no selector needed)
 export interface KeyboardCommand extends BaseCommand {
   action: 'keyboard';
-  keys: string; // e.g., "Control+a", "Shift+Tab"
+  subaction?: 'type' | 'press' | 'insertText'; // press kept for backward compat
+  keys?: string; // for legacy press path
+  text?: string; // for type/insertText
+  delay?: number; // for type (ms between keystrokes)
 }
 
 // Mouse wheel