Unifies PandaScript syntax by replacing uppercase keywords with slash
commands (e.g., `/goto`, `/click`, `/fill`). Refactors the `Command`
representation to use a generic tool call structure backed by schemas.
BREAKING CHANGE: Uppercase PandaScript keywords (GOTO, CLICK, TYPE, etc.)
are no longer supported. All scripts must use slash commands.
Adds the `-a` short flag, improves CLI validation for one-shot mode,
and ensures `--model` takes precedence over `--pick-model`.
BREAKING CHANGE: `--task-attachment` has been renamed to `--attach`.
Updates the agent tutorial to explain the JSON schema grammar for the
EXTRACT command, including selectors, attributes, and nested fields.
Adds examples for multi-line input and clarifies recording behavior.
