Add standard .claude scaffolding and inbox-check line

Create .claude/settings.json so shared project config is committable, add the deny-by-default .claude/* and .env.* allow-list block to .gitignore, and add the portable inbox-check line to AGENTS.md. Track Jitsi support in ROADMAP.

.gitignore

@@ -23,4 +23,15 @@ Config/Signing.xcconfig
 
 # Local env files (e.g. SPARK_BACKEND_URL for dev/harness runs) — never commit
 .env
-.env.local
+.env.*
+!.env.example
+
+# Claude Code — deny by default, allow-list shared wiring.
+# .claude/ also accumulates worktrees, editor configs, and OS cruft; commit
+# only the shared parts so new local scratch (or a stray secret) stays out.
+.claude/*
+!.claude/rules/
+!.claude/agents/
+!.claude/commands/
+!.claude/skills/
+!.claude/settings.json