fix: revert well-known/skills to middleware approach

[onmax]

#634 broke /.well-known/skills endpoints. Nitro's file-based routing interprets .well-known-skills.ts as a filename, generating wrong URL patterns:

• Generated: /:pkg/.well-known-skills
• Expected: /:pkg/.well-known/skills/**

Broken URLs (prod):

• https://npmx.dev/claude-skills-frontend/.well-known/skills/index.json → 404
• https://npmx.dev/claude-skills-frontend/.well-known-skills → 500

Fixed URLs (preview):

• https://npmxdev-git-fork-onmax-fix-well-known-skills-routing-poetry.vercel.app/claude-skills-frontend/.well-known/skills/index.json

This reverts to the middleware approach from #630 which uses regex matching to handle the path correctly. ISR caching rules in nuxt.config.ts remain unchanged.

Why two handlers?

Middleware runs on every request, so we need:

1. Outer defineEventHandler - checks URL match, returns undefined for non-matching paths (passes through to Nuxt)
2. Inner defineCachedEventHandler - only caches matching requests

Routes could use a single defineCachedEventHandler because file-based routing only sends matching URLs to that handler.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
npmx.dev	Ready	Preview, Comment	Feb 1, 2026 0:17am

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