chore: initial commit

Add project scaffolding: CLAUDE.md, PLAN.md, README.md, flake.nix, and go.mod.

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

CLAUDE.md

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+# Oubliette
+
+SSH honeypot written in Go. See `PLAN.md` for full project plan and architecture.
+
+## Development
+
+- **Nix devshell:** Always use `nix develop -c` to run commands, e.g. `nix develop -c go test ./...`, `nix develop -c golangci-lint run`.
+- **Tech stack:** Go, SQLite, x/crypto/ssh, Go templates + htmx for web UI. Single binary with embedded assets.
+
+## Guidelines
+
+- Write tests for all important functionality.
+- Update `README.md` when new features are added. Keep entries concise for minor stuff.
+- Keep code simple and focused. Refer to `PLAN.md` for design decisions.
+
+## Git workflow
+
+- Use **conventional commits** (e.g. `feat:`, `fix:`, `refactor:`, `docs:`, `test:`, `chore:`).
+- Check out a **feature branch** before starting work on a new feature.