feat: Initial attempt at wrapping Runtime in a worker within shell.

[jsantell]

Summary by cubic

Runs the Runtime inside a Web Worker and wires the shell to it, moving recipe execution off the main thread and keeping the UI responsive. Introduces a cell proxy and duck-typed cells so existing reactive code keeps working.

• New Features

  • Worker-based runtime with RuntimeWorker (main thread), worker script, and a typed IPC protocol.
  • RemoteCell (cell proxy) provides a cell-like interface across the worker; added CELL_MARKER and isCellLike for duck-typing.
  • Runner now exports ./worker and ./worker-script for integration.
  • Shell integrates the worker via RuntimeWorker and CharmHandle; added worker-friendly pattern factory helpers.
  • Worker emits console, navigate, and error events to the shell.
  • Identity.derive() accepts optional config to choose key implementation (used for Deno-friendly key serialization).

• Migration

  • Prefer isCellLike over isCell in consumers; effect/render updated accordingly.
  • To adopt the worker: import RuntimeWorker from @commontools/runner/worker, await ready(), use getCellFromLink for RemoteCell, and dispose() when done.
  • UI changes: CharmController → CharmHandle; runtimeContext now provides RuntimeWorker and space DID.
  • Temporarily disabled features pending IPC: Favorites and ACL; one iframe counter test remains disabled; Outliner UI temporarily excluded.

^{Written for commit 9093dfd. Summary will update automatically on new commits.}