Add CLAUDE.md for Claude Code onboarding (#743)

Provides build/test commands, architecture overview, and key conventions
so future Claude Code sessions can be productive immediately.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Plano is an AI-native proxy server and data plane for agentic applications, built on Envoy proxy. It centralizes agent orchestration, LLM routing, observability, and safety guardrails as an out-of-process dataplane.
+
+## Build & Test Commands
+
+### Rust (crates/)
+
+```bash
+# Build WASM plugins (must target wasm32-wasip1)
+cd crates && cargo build --release --target=wasm32-wasip1 -p llm_gateway -p prompt_gateway
+
+# Build brightstaff binary (native target)
+cd crates && cargo build --release -p brightstaff
+
+# Run unit tests
+cd crates && cargo test --lib
+
+# Format check
+cd crates && cargo fmt --all -- --check
+
+# Lint
+cd crates && cargo clippy --locked --all-targets --all-features -- -D warnings
+```
+
+### Python CLI (cli/)
+
+```bash
+cd cli && uv sync              # Install dependencies
+cd cli && uv run pytest -v     # Run tests
+cd cli && uv run planoai --help  # Run CLI
+```
+
+### JavaScript/TypeScript (apps/, packages/)
+
+```bash
+npm run build      # Build all (via Turbo)
+npm run lint       # Lint all
+npm run dev        # Dev servers
+npm run typecheck  # Type check
+```
+
+### Pre-commit (runs fmt, clippy, cargo test, black, yaml checks)
+
+```bash
+pre-commit run --all-files
+```
+
+### Docker
+
+```bash
+docker build -t katanemo/plano:latest .
+```
+
+### E2E Tests (tests/e2e/)
+
+E2E tests require a built Docker image and API keys. They run via `tests/e2e/run_e2e_tests.sh` which executes three test suites: `test_prompt_gateway.py`, `test_model_alias_routing.py`, and `test_openai_responses_api_client_with_state.py`.
+
+## Architecture
+
+### Core Data Flow
+
+Requests flow through Envoy proxy with two WASM filter plugins, backed by a native Rust binary:
+
+```
+Client → Envoy (prompt_gateway.wasm → llm_gateway.wasm) → Agents/LLM Providers
+                              ↕
+                         brightstaff (native binary: state, routing, signals, tracing)
+```
+
+### Rust Crates (crates/)
+
+All crates share a Cargo workspace. Two compile to `wasm32-wasip1` for Envoy, the rest are native:
+
+- **prompt_gateway** (WASM) — Proxy-WASM filter for prompt/message processing, guardrails, and filter chains
+- **llm_gateway** (WASM) — Proxy-WASM filter for LLM request/response handling and routing
+- **brightstaff** (native binary) — Core application server: handlers, router, signals, state management, tracing
+- **common** (library) — Shared across all crates: configuration, LLM provider abstractions, HTTP utilities, routing logic, rate limiting, tokenizer, PII detection, tracing
+- **hermesllm** (library) — Translates LLM API formats between providers (OpenAI, Anthropic, Gemini, Mistral, Grok, AWS Bedrock, Azure, together.ai). Key types: `ProviderId`, `ProviderRequest`, `ProviderResponse`, `ProviderStreamResponse`
+
+### Python CLI (cli/planoai/)
+
+The `planoai` CLI manages the Plano lifecycle. Key commands:
+- `planoai up <config.yaml>` — Validate config, check API keys, start Docker container
+- `planoai down` — Stop container
+- `planoai build` — Build Docker image from repo root
+- `planoai logs` — Stream access/debug logs
+- `planoai trace` — OTEL trace collection and analysis
+- `planoai init` — Initialize new project
+
+Entry point: `cli/planoai/main.py`. Container lifecycle in `core.py`. Docker operations in `docker_cli.py`.
+
+### Configuration System (config/)
+
+- `arch_config_schema.yaml` — JSON Schema (draft-07) for validating user config files
+- `envoy.template.yaml` — Jinja2 template rendered into Envoy proxy config
+- `supervisord.conf` — Process supervisor for Envoy + brightstaff in the container
+
+User configs define: `agents` (id + url), `model_providers` (model + access_key), `listeners` (type: agent/model/prompt, with router strategy), `filters` (filter chains), and `tracing` settings.
+
+### JavaScript Apps (apps/, packages/)
+
+Turbo monorepo with Next.js 16 / React 19 applications and shared packages (UI components, Tailwind config, TypeScript config). Not part of the core proxy — these are web applications.
+
+## Key Conventions
+
+- Rust edition 2021, formatted with `cargo fmt`, linted with `cargo clippy -D warnings`
+- Python formatted with Black
+- WASM plugins must target `wasm32-wasip1` — they run inside Envoy, not as native binaries
+- The Docker image bundles Envoy + WASM plugins + brightstaff + Python CLI into a single container managed by supervisord
+- API keys come from environment variables or `.env` files, never hardcoded