The signals-dashboard canvas extension bundles with the-workshop
plugin (x-awesome-copilot.extensions), so installing the plugin from
awesome-copilot includes the dashboard. Drop the pointers telling
users to install from jennyf19/the-workshop.
Addresses PR review comments on README (Cairn Dashboard section),
signal-write SKILL note, and workshop-ta agent viewing-signals note.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 26faf13e-639c-4a21-ac05-c0dc2bff7c62
