Markdown Upgrade

Take an existing plain markdown file and redesign it visually. The argument (or the user's message) names the file; if no file is named, ask which one or look for the obvious candidate (e.g. the README, or the .md file just discussed).

Process

1. Read the entire file first. Never upgrade a file you've partially read.
2. Load the design system: read ../markdown-design/SKILL.md and use its structure→element mapping. Pull exact syntax from its references/ files as needed.
3. Inventory upgrade opportunities — walk the doc and mark:
   • Prose describing a process/flow → flowchart or sequence diagram
   • Prose comparing options or listing ≥3 parallel facts → table
   • "Note that…", "Be careful…", "Make sure…" paragraphs → alerts with correct severity
   • Long code/log/config blocks that aren't the main point → collapsible <details>
   • Lists of dates/phases → gantt or timeline
   • Status words scattered in prose → ✅ 🔄 ❌ markers or a status table
   • Missing summary line under the title, missing TOC on long docs → add them
4. Rewrite the file (Edit/Write) applying the upgrades.
5. Report a short summary: which sections became diagrams/tables/alerts, one line each.