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>

skills/video/references/ai-video-prompting.md

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+# AI Video Prompting Guide
+
+How to write effective prompts for AI video generation models (Veo, Runway, Kling, Pika).
+
+---
+
+## Prompt Structure
+
+A strong video prompt follows this formula:
+
+```
+[Subject] + [Action] + [Camera movement] + [Visual style] + [Lighting/mood] + [Technical specs]
+```
+
+### Example Prompts by Use Case
+
+**Product hero shot:**
+```
+A sleek laptop on a minimal white desk, screen glowing with a dashboard UI,
+camera slowly orbits 180 degrees around the desk,
+soft volumetric lighting from the left, shallow depth of field,
+cinematic commercial aesthetic, 4K
+```
+
+**Lifestyle B-roll:**
+```
+A woman in a modern co-working space smiling while looking at her phone,
+natural window light, candid documentary feel,
+camera handheld with subtle movement, warm color grading
+```
+
+**Abstract/brand:**
+```
+Flowing liquid gold particles forming the shape of a network graph,
+dark background, particles catch light as they move,
+slow-motion macro photography style, dramatic rim lighting
+```
+
+**SaaS explainer scene:**
+```
+An overhead shot of a team around a conference table pointing at charts,
+camera slowly pushes in, bright modern office,
+clean corporate style, even lighting, 1080p
+```
+
+---
+
+## Camera Movement Vocabulary
+
+Use these terms — video models understand them:
+
+| Term | Effect |
+|------|--------|
+| **Static** | Locked camera, no movement |
+| **Pan left/right** | Camera rotates horizontally |
+| **Tilt up/down** | Camera rotates vertically |
+| **Dolly in/out** | Camera moves toward/away from subject |
+| **Orbit** | Camera circles around subject |
+| **Tracking shot** | Camera follows moving subject |
+| **Crane/aerial** | Camera rises or descends |
+| **Handheld** | Subtle shake, documentary feel |
+| **Zoom** | Lens zoom (different from dolly) |
+| **Slow push** | Gradual dolly in — builds tension/focus |
+
+---
+
+## Style Keywords
+
+### Cinematic
+- "cinematic color grading"
+- "anamorphic lens flare"
+- "shallow depth of field"
+- "film grain"
+- "35mm film"
+
+### Commercial/Corporate
+- "clean commercial lighting"
+- "bright and airy"
+- "professional corporate aesthetic"
+- "even, diffused lighting"
+
+### Documentary
+- "handheld documentary style"
+- "natural lighting"
+- "candid, unposed"
+- "observational camera"
+
+### Social/Trendy
+- "vertical 9:16"
+- "fast-paced cuts"
+- "bold text overlays"
+- "high contrast, saturated colors"
+
+---
+
+## Model-Specific Tips
+
+### Veo (Google)
+
+- Excels at photorealism and complex scenes
+- Supports audio generation synced to video
+- Best with detailed, descriptive prompts
+- Specify "4K" or "high resolution" for max quality
+- Can handle multiple subjects and scene transitions
+
+### Runway Gen-4
+
+- Strong motion control — specify camera movements precisely
+- Best temporal consistency (subjects stay consistent across frames)
+- Use motion brush for specific area animation
+- Image-to-video works well — provide a reference frame
+- Keep prompts under 100 words for best results
+
+### Kling
+
+- Can generate up to 2 minutes (much longer than others)
+- Good for longer narrative sequences
+- More affordable for bulk generation
+- Quality drops slightly at longer durations
+- Best with simpler scenes and fewer subjects
+
+### Pika
+
+- Fastest generation time (under 2 minutes)
+- Good for quick iterations and experimentation
+- Effects mode adds motion to still images
+- Best for short clips (5-15 seconds)
+- Less control over camera movement
+
+---
+
+## Common Prompt Mistakes
+
+| Mistake | Why It Fails | Fix |
+|---------|-------------|-----|
+| "A person using our app" | Too vague, no visual detail | Describe the person, setting, lighting, camera |
+| Including text/logos | AI can't render readable text | Add text in post via Hyperframes/CapCut |
+| "Make it viral" | Not a visual instruction | Describe the visual style you want |
+| Extremely long prompts (200+ words) | Models lose focus | Keep to 50-100 words, be specific |
+| No camera direction | Random/static camera | Always specify movement or "static" |
+| "Realistic" alone | Not specific enough | "Photorealistic, natural lighting, shot on RED camera" |
+
+---
+
+## Prompting Workflow
+
+1. **Reference first** — find a real video that looks like what you want
+2. **Describe it** — break down: subject, action, camera, style, mood
+3. **Generate 3-4 variations** — same concept, different angles or styles
+4. **Iterate on the best** — refine the prompt based on results
+5. **Composite** — combine AI footage with programmatic text/overlays
+
+---
+
+## Aspect Ratios
+
+Always specify in your prompt or generation settings:
+
+| Platform | Ratio | Resolution |
+|----------|-------|-----------|
+| YouTube | 16:9 | 1920x1080 or 3840x2160 |
+| TikTok/Reels/Shorts | 9:16 | 1080x1920 |
+| Instagram Feed | 1:1 or 4:5 | 1080x1080 or 1080x1350 |
+| Website hero | 16:9 | 1920x1080 |
+| LinkedIn | 16:9 or 1:1 | 1920x1080 |
+
+---
+
+## Cost Optimization
+
+- **Iterate at low resolution** — upscale only the final version
+- **Use Kling for drafts** — cheapest per second, switch to Veo/Runway for finals
+- **Image-to-video** — providing a reference frame saves generation credits and gives better results
+- **Batch similar prompts** — models often offer volume discounts
+- **Cache and reuse** — B-roll clips can be reused across multiple videos