feat: improve skill scores and add Tessl review workflow

[rohan-tessl]

Hey @Zidong-IA 👋

I ran your skills through tessl skill review at work and found some targeted improvements.

Here's the full before/after:

Skill	Before	After	Change
infinite-gratitude	16%	79%	+63%
fal-upscale	24%	94%	+70%
seo-fundamentals	35%	90%	+55%
market-sizing-analysis	36%	100%	+64%
avalonia-zafiro-development	48%	94%	+46%

This PR intentionally caps changes at five skills to keep the review manageable. The included GitHub Action workflow (see below) will surface Tessl feedback on future SKILL.md changes across the entire library.

Changes summary

• infinite-gratitude: Expanded from a stub with no actionable content to a structured skill with workflow steps, agent role table, and output format specification. Added concrete "Use when" triggers and natural language keywords.
• fal-upscale: Replaced placeholder text with executable Python and curl API examples, model comparison table, parameter reference, and setup instructions. Added specific trigger terms for natural user queries.
• seo-fundamentals: Transformed from a conceptual reference document into an actionable audit workflow with a technical checklist, schema markup examples, Core Web Vitals fix guidance, and explicit trigger terms.
• market-sizing-analysis: Condensed from 424 lines of verbose explanation to 105 lines of lean, formula-focused content with a complete worked example (AI Email Marketing SaaS), validation red flags table, and industry-specific formulas. Preserved references to existing references/ and examples/ directories.
• avalonia-zafiro-development: Added concrete C# code examples for DynamicData pipelines and Result-based error handling. Enhanced description with specific trigger terms (.axaml, Zafiro, Avalonia). Added verification step to the workflow. Preserved all existing guide references.

All skills now have:

• Proper "Use when" clauses with natural trigger terms
• Third-person description format
• Concrete examples or executable code
• Clear workflow steps

Tessl Skill Review GitHub Action

This PR also adds .github/workflows/skill-review.yml — a lightweight GitHub Action that runs automatically on PRs that touch any SKILL.md file.

• What it does: Runs tesslio/skill-review on changed SKILL.md files and posts a single PR comment with scores and feedback (updated on each push).
• Zero extra accounts: Contributors don't need a Tessl login — only the default GITHUB_TOKEN is used.
• Non-blocking by default: The check is feedback-only with no surprise red CI. Add with: fail-threshold: 70 later if you want a hard gate.
• Not a build replacement: This is review automation for skill markdown quality, not a substitute for your existing validation/build pipeline (npm run validate, etc.).
• Why only five skills here: Capping manual optimization keeps this PR reviewable. After merge, every future PR that touches SKILL.md gets automatic review comments — so the rest of the library improves incrementally.

Honest disclosure — I work at @tesslio where we build tooling around skills like these. Not a pitch — just saw room for improvement and wanted to contribute.

Want to self-improve your skills? Just point your agent (Claude Code, Codex, etc.) at this Tessl guide and ask it to optimize your skill. Ping me — @rohan-tessl — if you hit any snags.

Thanks in advance 🙏