Add audio-tldr (Creative & Media)

[AugustusW (AugustusW)]

Adds audio-tldr — a Claude Code skill that summarizes videos, audio files, and podcasts into key takeaways.

Checklist vs. contribution guidelines:

• Real use case: built for daily podcast/YouTube triage; shipped and in daily use
• Well-documented: bilingual README (EN/zh-TW), quickstart, platform matrix (macOS/Linux/Windows)
• Tested: automated test suite, tagged releases (currently v0.4.0), MIT licensed
• Distinctive vs. existing entries: transcription runs locally (Whisper/mlx-whisper — audio never leaves the machine) and transcripts are cached, so repeat requests skip re-transcription entirely