Saving an enabled plugin threw away hot_reload_plugin's (ok, message), so a
plugin that failed to load live read "Enabled, not loaded" with nothing
more. Now:
- a live-load failure is recorded with its reason, as a boot failure is, and
logged; a later success clears it;
- any save of an enabled plugin that isn't running tries to start it, not
only the off-to-on toggle;
- enabling one already running is a success, not a failure;
- the plugin's page offers "Restart to load" while it is enabled and not
running.
Quart never marks the app as having served its first request, so
register_blueprint after startup is allowed: hot-loading is not refused
wholesale, as #6087 suspected.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
