add digest command and update monthly digest
- add .claude/commands/digest.md for portable digest generation
- update index.html with complete dec-jan digest in collapsible details
- added: follower-weight, zql, hello-tinker, atproto, marvin
- uses <details> for unobtrusive display
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>