docs(skills): salvage dropped trigger content into skill bodies

For 14 of 74 compressed skills, the original description contained
trigger keywords, technique counts, attribution, or use-case phrases
not covered by the existing body content. Prepends a 'When to use' /
'What's inside' block near the top so the agent still has the full
context when the skill is loaded.

Skills salvaged:
- codex, ascii-video, creative-ideation, excalidraw, manim-video, p5js
- gif-search, heartmula, youtube-content
- lm-evaluation-harness, obliteratus, vllm, axolotl
- powerpoint

Remaining 60 skills were verified to already cover the dropped content
in their existing body sections (When to Use, overview, intro prose)
or had short descriptions fully captured by the new compressed form.

skills/media/gif-search/SKILL.md

@@ -16,6 +16,10 @@ metadata:
 
 Search and download GIFs directly via the Tenor API using curl. No extra tools needed.
 
+## When to use
+
+Useful for finding reaction GIFs, creating visual content, and sending GIFs in chat.
+
 ## Setup
 
 Set your Tenor API key in your environment (add to `~/.hermes/.env`):