* feat(plugins): unify source installation and simplify plugin settings
* feat(plugins): install npm sources and review CLI updates
Treat install selectors as one-time choices. Keep source identity separate from the installed revision, and resolve ordinary updates from the current upstream default. npm only acquires directories; plugin loading remains independent of npm.
* fix(plugins): preserve CLI diagnostics and exercise reviewed updates
Move new source capability coverage to real browser journeys. Update the requirements regression to exercise preview and apply, and preserve the existing duplicate-selector diagnostic across positional option scopes.
* test(plugins): remove unused pending helper
* test(plugins): pack registry fixtures with the Windows command runner
* test(plugins): assert failed client contribution setup
* docs(plugins): consolidate guides and document npm publishing
* docs(plugins): introduce publishing choices before npm instructions
* test(plugins): own browser journey cleanup in a fixture
* feat(plugins): prepare scaffolded packages for publishing
Accept plugin requirements against the runtime version or its stable core while preserving the legacy version boundary. Validate all example manifests, correct the ACP example metadata, and prepare plugin author documentation for the beta.