Update an existing documentation file in .chalk/docs/.

Workflow

Find the doc — Search .chalk/docs/ for the file matching $ARGUMENTS. Match by filename, path, or content. If ambiguous, list candidates and ask the user to clarify.
Read current content — Load the file to understand what exists.
Apply changes — Update the content per the user's request. Preserve existing structure and sections where possible. Don't remove content unless explicitly asked.
Update the "Last updated" line — Set to today's date with a brief change note describing what changed.
Write the file — Save back to the same path.
Confirm — Tell the user what was changed and the file path.

Rules

Preserve structure — Keep existing # and ## headings intact unless the user asks to reorganize.
Update, don't rewrite — Modify the specific sections relevant to the change. Don't rewrite unrelated content.
Last updated is required — Always update the date line. Format: Last updated: YYYY-MM-DD (<brief change note>).
No frontmatter — Docs are plain markdown. Don't add YAML frontmatter.
Respect the vertical's tone — Product docs are business-facing, AI docs are agent-facing reference-style, Engineering docs are technical and comprehensive.