Add TikTok video skills (caption-animation, countdown-video, lower-thirds, short-form-video)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011XhxckAYjGMLrLECWuKBzg

.agents/skills/countdown-video/README.md

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+# Countdown Video
+
+Make a countdown that ends exactly when it should. The whole craft is one idea: derive the remaining time from the frame (or a monotonic timestamp), then format and animate that number — never count down with a `setInterval`. Covers livestream "starting soon" screens, launch and flash-sale countdowns, and looping backgrounds. For creators who need a timer that lands on zero on the exact frame.
+
+## When it activates
+
+- "Make a countdown timer video" or "create a countdown animation."
+- "Build a stream starting soon countdown" or "do an event/launch/sale countdown."
+- "Animate a mm:ss or dd:hh:mm:ss timer."
+- "Add digit roll/flip transitions to a counter" or "loop a countdown background."
+
+## Example prompts
+
+- "Build a 10-minute 'be right back' livestream countdown."
+- "Make a dd:hh:mm:ss launch countdown to a fixed target date."
+- "Add flip transitions to an mm:ss timer that hits zero on the exact frame."
+
+## What's inside
+
+- `SKILL.md` — frame-accurate (drift-free) timers, time formatting, and a configurable duration prop.
+- `references/countdown-cookbook.md` — recipes for common countdown scenarios.
+- `references/digit-flip.md` — digit flip/roll transition techniques.
+
+---
+Part of **[Short-Form Video Skills](../../)** · Built by **[iart.ai](https://iart.ai/?utm_source=github&utm_medium=readme&utm_campaign=tiktok-video-skills&utm_content=skill_footer&utm_term=countdown-video)** — the AI motion agent for editable, on-brand motion graphics.