- MCP: execute, batch, type_text, select_text, get_text, inspect_document,
render_page and save_document take an optional doc (an open document's
id); the headless server runs them through Session::with_document and
the bridge passes doc to the app. New list_documents tool; new_document
replies with the new document's id. Tool descriptions and the server
instructions say that file.new and file.open open another document.
- Control channel: engine.execute, document.inspect and ui.render take
doc and work on that document while the window keeps the active one;
file.close on an addressed document refuses unsaved changes unless
forced; ui.* commands need the document on screen. ui.inspect reports
document and documents. Unknown or malformed ids are errors.
- CLI run starts with one open document; help and docs describe how
file.new, file.open and view.switchWindows work in a run.
- docs/mcp.md and docs/control-protocol.md describe document ids and doc.
