feat: discover Oh My Pi skills natively

An Oh My Pi pane listed no skills at all: the palette only knew the skill
directories named in the relay's own INI, and omp has thirteen sources.

Reproduce omp's own resolution - every source in descending priority with
first-wins dedupe, so the shared file budget is spent on the sources that win -
and honour omp's own bans by reading the enable toggles, disabledExtensions,
ignoredSkills and includeSkills from its config.yml, at the user level and then
overlaid by any repo-level .omp config. A skill the user has banned in omp does
not appear in the palette. The relay's configured skill directories still take
precedence, so an explicitly configured pane behaves exactly as before.

The settings parser reads the constrained YAML subset these keys actually use
and fails open: an unreadable or unparsable config registers the commands
rather than hiding them, because a hidden command is worse than an extra one.