Add CLAUDE.md with static project context

Covers pipeline architecture, file map, key decisions, coding conventions,
and how to syntax-check. Points to TODO.md, CHANGELOG.md, and SERVICES.md
for dynamic information. Also removes CLAUDE.md from .gitignore.

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

.gitignore

@@ -1,8 +1,5 @@
 # HOPS .gitignore
 
-# Claude Code development documentation
-CLAUDE.md
-
 # Log files
 *.log