chore: add CLAUDE.md and update gitignore

.gitignore

@@ -35,3 +35,4 @@ config.local.yaml
 state/
 checkpoints/
 tmp/
+.agent-queue/

CLAUDE.md

@@ -0,0 +1,26 @@
+# Claude Failover — Developer Guide
+
+## Project
+
+Go daemon for Claude Code multi-account session orchestration with automatic quota-based failover.
+Public repo — NO sensitive info (IPs, internal paths, credentials, product names).
+
+## Stack
+
+- Go 1.22+
+- tmux (via exec.Command)
+- SQLite (checkpoints)
+- YAML config
+- HTTP API (net/http)
+
+## Architecture
+
+See docs/architecture.md for full design.
+
+## Rules
+
+- All paths must be configurable (no hardcoded /home/ubuntu)
+- Use interfaces for tmux, filesystem (testable)
+- Single binary, no external dependencies at runtime
+- Config via YAML only (no .env)
+- git push after every task