Syncs a CLAUDE.md file with Hologram AI rules.
The content is read from the usage-rules.md file shipped with the Hologram
package and wrapped in <!-- hologram-start --> / <!-- hologram-end --> markers.
If the target file already exists:
- If markers are found, the content between them is replaced.
- If no markers are found, the marked section is appended at the end.
If the target file doesn't exist, it is created with the marked section.
$ mix holo.gen.claude_md