Track CLAUDE.md and update it to match the current architecture

The previous (untracked) CLAUDE.md described ChatViewModel as a ~170KB
class split into +Nostr/+PrivateChat/+Tor extension files. Reality:
ChatViewModel.swift is ~1,600 lines and delegates to ~25 coordinator/
pipeline types in bitchat/ViewModels/; the Extensions/ files are thin
delegation shims. Document the actual structure: AppRuntime as the
composition root, ConversationStore as the single-writer message
store, the BLE handler/policy collaborators around BLEService, and
BinaryProtocol's move into the BitFoundation local package.

Also start tracking CLAUDE.md (removing its .gitignore entry) so the
guidance stays versioned alongside the code it describes; build/test
command sections are unchanged.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -6,7 +6,6 @@
 plans/
 
 ## AI
-CLAUDE.md
 AGENTS.md
 .claude/