feat: add /media skill — story mining and launch narratives

[HMAKT99]

The feature shipped. Now someone needs to write the blog post.

Engineering ships fast. Marketing can't keep up. The feature is live but there's no press release, no blog post, no tweet thread. The story is buried in commit messages.

What /media does

You:   /media --launch photo-upload

Claude: STORY ANGLES (ranked by newsworthiness)
        1. "Product X turns one photo into a complete listing in 3 seconds"
           Hook: AI-powered listing creation, not just photo upload
        2. "How we built a product-recognition pipeline in 2 weeks"
           Hook: Engineering deep-dive for Hacker News

        PRESS RELEASE DRAFT:
        HEADLINE: Product X Now Creates Complete Listings From a Single Photo
        LEDE: Sellers upload one photo. AI identifies the product, pulls
        specs, drafts the title and description, suggests pricing...

        TWEET THREAD:
        1/ We just shipped something wild: upload a photo of anything
           you want to sell, and we create the entire listing for you.
        2/ How it works: photo → product recognition → spec lookup →
           description generation → pricing comps. 3 seconds total.
        ...

Mines git history for stories. Crafts launch narratives, press releases, blog post drafts, tweet threads. Every claim verified against the actual code.

Only .tmpl committed — bun run gen:skill-docs generates the rest.

Test plan

• .tmpl follows template pipeline
• Registered in gen-skill-docs.ts, skill-check.ts, test files