fix(writing-skills): correct false 'only two fields' frontmatter claim (#882)

[arittr]

What problem are you trying to solve?

The writing-skills skill claims only name and description frontmatter fields are supported, when Claude Code actually supports additional fields. This causes every skill Claude creates to have incomplete frontmatter.

What does this PR change?

Corrects the false claim about supported frontmatter fields in the writing-skills skill documentation.

Closes #882

🤖 Generated with Claude Code

[arittr]

This change is part of the following stack:

• docs(codex-tools): add named agent dispatch mapping for Codex #900
  • fix(writing-skills): correct false 'only two fields' frontmatter claim (#882) #902 ◀
    • fix(subagent-prompts): instruct subagents to read CLAUDE.md for project conventions #899
      • feat: Codex App worktree and sandbox compatibility #901

_{Change managed by git-spice.}