feat(claude/commands): add claude-to-agents conversion command

Provide a reusable command to convert a project's CLAUDE.md into an
AGENTS.md file while replacing the original with a thin @-reference.
Includes precondition checks, self-reference updating, and summary
reporting steps.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

claude/commands/claude-to-agents.md

@@ -0,0 +1,36 @@
+# Task: Convert CLAUDE.md to AGENTS.md
+
+Convert this project's `CLAUDE.md` into an `AGENTS.md` file, and
+replace `CLAUDE.md` with a thin reference to it.
+
+## Steps
+
+1. **Verify preconditions**:
+   - Confirm `CLAUDE.md` exists in the project root. If not, abort
+     with an error message.
+   - Confirm `AGENTS.md` does NOT already exist in the project root.
+     If it does, abort — suggest using it directly or removing it
+     first.
+
+2. **Read `CLAUDE.md`** content in full.
+
+3. **Review content for references that need updating**:
+   - Headings like `# CLAUDE.md` → `# AGENTS.md`
+   - Self-references like "this CLAUDE.md file" →
+     "this AGENTS.md file"
+   - Any other mentions of the filename that refer to the file
+     itself and should change to reflect the new name
+   - Do NOT change references to CLAUDE.md that refer to other
+     projects' files, Claude Code documentation, or external
+     concepts
+
+4. **Write `AGENTS.md`** with the updated content.
+
+5. **Replace `CLAUDE.md`** contents with just:
+   ```
+   @AGENTS.md
+   ```
+   This makes Claude Code load `AGENTS.md` via the `@`-reference.
+
+6. **Summary**: Report what was done, including any references that
+   were updated in step 3.