feat: add video skill for AI video production (#258)

* feat: add video skill for AI video production

New skill covering programmatic video (Remotion, Hyperframes), AI video
generation (Veo, Runway, Kling), AI avatars (HeyGen, Synthesia), and
editing/repurposing workflows. Includes AI video prompting reference.

New tool integrations: HeyGen (MCP-enabled), Hyperframes (open source).
Updated tools registry with Video category expansion.

Total skills: 39

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: apply accuracy fixes from Codex review

- Hyperframes: Node.js requirement 18+ → 22+ (confirmed via npm)
- Veo 3: soften 4K claim to "Up to 1080p (4K varies)"
- Sora: replace shutdown claim with availability caveat
- HeyGen: remove dollar amounts, link to pricing page
- Remotion: soften license wording

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -12,7 +12,7 @@
   "plugins": [
     {
       "name": "marketing-skills",
-      "description": "38 marketing skills for technical marketers and founders: ASO, CRO, copywriting, cold email, SEO, AI SEO, paid ads, ad creative, churn prevention, pricing strategy, referral programs, revenue operations, sales enablement, customer research, site architecture, and more",
+      "description": "39 marketing skills for technical marketers and founders: ASO, CRO, copywriting, cold email, SEO, AI SEO, paid ads, ad creative, video production, churn prevention, pricing strategy, referral programs, revenue operations, sales enablement, customer research, site architecture, and more",
       "source": "./"
     }
   ]