sync-agent-instructions

# Sync Agent Instructions Keep CLAUDE.md, GEMINI.md, and AGENTS.md in sync so all AI coding tools share the same project instructions. ## Workflow 1. **Detect changes** — Run `git diff HEAD -- CLAUDE.md GEMINI.md AGENTS.md` to see which file(s) have uncommitted changes. 2. **Determine source file:** - **One file changed** — That file is the source. Copy its content to the other two. - **Multiple files changed** — Ask the user which file to use as the source. - **No files changed** — Compare all three with `diff`. If they differ, report which sections differ and ask the user which file to use as source. If identical, report "All instruction files are in sync." and stop. 3. **Sync** — Read the source file and write its exact content to the other two files. 4. **Stage** — Run `git add` on the two modified files. 5. **Report** — Tell the user which file was the source and that the other two have been updated.