#5273: fix: skill frontmatter fixes + description improvements (35 skills)

## Summary Fix broken YAML frontmatter in 3 skills and improve descriptions across 32 skills for better trigger accuracy. ### Structural Fixes - **canvas**: Add missing YAML frontmatter (had no `---` delimiters at all) - **discord**: Quote description to fix YAML colon-in-value parse error (`discord tool: send` parsed as nested mapping) - **food-order**: Quote description to fix same YAML colon-in-value issue (`Triggers: order food`) These work at runtime due to OpenClaw's dual parser (YAML + line-by-line fallback), but fail any standard YAML parser including the skill-creator's own validator. ### Description Improvements (32 skills) Expanded short descriptions (<15 words) to 30-40 words with `Use when...` trigger contexts. The `description` field in frontmatter is the primary trigger mechanism — it's how the AI decides when to load a skill. Short descriptions miss activations. **Before:** ``` description: Get current weather and forecasts (no API key required). ``` **After:** ``` description: Get current weather, detailed forecasts, and conditions for any location using free APIs (wttr.in or Open-Meteo) without API keys or registration. Use when you want to check weather, temperature, rain, forecasts, or what to wear without API setup overhead. ``` Skills updated: bear-notes, bird, blogwatcher, blucli, camsnap, eightctl, gemini, gifgrep, gog, imsg, local-places, nano-banana-pro, nano-pdf, notion, obsidian, openai-image-gen, openai-whisper, openai-whisper-api, openhue, ordercli, peekaboo, sag, session-logs, sherpa-onnx-tts, songsee, sonoscli, spotify-player, tmux, trello, video-frames, voice-call, weather ### How this was found Built an automated [skill-evaluator](https://github.com/Terwox/openclaw/tree/fix/skill-frontmatter-and-descriptions) that checks structural quality, frontmatter validity, description length, trigger phrases, credential scanning, and more. Ran it across all 50+ bundled skills. ### Testing - All 35 modified files pass `yaml.safe_load()` - All descriptions are 30+ words with trigger context - No functional changes — description-only edits + frontmatter quoting <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR fixes broken YAML frontmatter for `canvas`, `discord`, and `food-order`, and expands the `description` frontmatter field across ~32 skills to improve skill-trigger accuracy. These are documentation/frontmatter-only changes; they don’t modify runtime code paths, but they do improve compatibility with standard YAML tooling and validators. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge; changes are limited to skill documentation/frontmatter. - Reviewed the diffs across all touched skill markdown files. Changes are confined to YAML frontmatter `description` edits and adding missing delimiters, with no executable code changes. The only issue found is a personal hostname in an example URL inside the Canvas skill doc, which is low-risk but should be sanitized for maintainability/privacy. - skills/canvas/SKILL.md <!-- greptile_other_comments_section --> _{(4/5) You can add custom instructions or style guidelines for the agent [here](https://app.greptile.com/review/github)!} <!-- /greptile_comment -->