docs(todo): drop head subcommand item

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

TODO.md

@@ -30,7 +30,6 @@
 
 ## Tooling
 
-- [ ] `head` subcommand — first N rows via `ScanOptions.limit`
 - [ ] String min/max in stats — requires utf8 scalar encoding in the proto
 
 ## Large-file support