v0.70.0 — skill install understands collections

skill install handles a repository that is a collection of skills

skill install assumed a repository is one skill: it cloned the source into
<skills-dir>/<name> and stopped. Claude and Kimi discover skills by scanning
exactly one level deep, so a repository whose skills live in subdirectories
landed every one of them a level too deep, where nothing would ever find them.

git clone still exited 0, so the install reported success — a green summary
over zero usable skills, with nothing to suggest otherwise.

Now the clone is inspected and resolved:

• a SKILL.md at the root is one skill, left exactly where it was cloned
• subdirectories holding SKILL.md are a collection: each is lifted beside
  its siblings and the wrapper removed, since the wrapper holds the
  repository's README, tooling and CI, none of which is a skill
• a clone with no SKILL.md anywhere is now a reported failure with that
  reason, instead of counting as installed

A skill whose name is already taken is left alone and reported, so an install
can never replace a skill you already had. Gemini installs natively and is
untouched by any of this.

Verified against a real 13-skill collection: 0 discoverable before, 13 after.

Moshpit

• Lifetime pricing: $5 an ending, $2 a name, paid once (#436)
• Backfill a Moshpit name with a clearnet twin (#435)

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Full changelog: v0.69.0...v0.70.0