docs: Add CLAUDE.md reference guide for AI assistants

- Quick project overview and architecture summary
- Links to key documentation (BLE_PROTOCOL_v2.2.md, README, etc.)
- Development workflow guidance
- File-by-function quick reference

Helps AI assistants quickly orient to the project without duplicating
existing documentation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

CLAUDE.md

@@ -0,0 +1,76 @@
+# Claude Code Reference Guide
+
+Quick reference for AI assistants working on the BLE-Reticulum project.
+
+## Project Overview
+
+A Bluetooth Low Energy (BLE) interface for [Reticulum Network Stack](https://reticulum.network), enabling mesh networking over BLE on Linux devices with BlueZ 5.x. Supports dual-mode operation (central + peripheral), multi-peer mesh networking, and automatic peer discovery.
+
+## Key Documentation
+
+### Protocol & Architecture
+- **[BLE_PROTOCOL_v2.2.md](BLE_PROTOCOL_v2.2.md)** - Complete protocol specification
+  - 5 comprehensive lifecycle sequence diagrams (Mermaid format)
+  - Configuration reference (13 parameters)
+  - Platform-specific workarounds (BlueZ patches)
+  - MAC sorting, identity handshake, fragmentation details
+  - Use this as the authoritative technical reference
+
+- **[REFACTORING_GUIDE.md](REFACTORING_GUIDE.md)** - Driver abstraction architecture
+  - Reference for implementing new platform drivers
+  - Explains `BLEDriverInterface` contract
+
+### User Documentation
+- **[README.md](README.md)** - Installation, quick start, troubleshooting
+- **[TESTING.md](TESTING.md)** - Test execution and procedures
+- **[CONTRIBUTING.md](CONTRIBUTING.md)** - Code style and PR process
+
+## Architecture
+
+**Main Components:**
+- `BLEInterface.py` - High-level Reticulum interface logic
+- `linux_bluetooth_driver.py` - Linux platform driver (Bleak + bluezero)
+- `bluetooth_driver.py` - Abstract driver interface
+- `BLEGATTServer.py` - Peripheral mode GATT server
+- `BLEFragmentation.py` - MTU-based packet fragmentation/reassembly
+
+**Driver Abstraction:** The interface uses a driver-based architecture to separate Reticulum protocol logic from platform-specific BLE implementations.
+
+## Current Status
+
+**Branch:** `refactor/abstraction-layer` (driver abstraction complete, awaiting merge)
+
+**Technologies:**
+- [Bleak](https://github.com/hbldh/bleak) - BLE central operations
+- [bluezero](https://github.com/ukBaz/python-bluezero) - GATT server (peripheral mode)
+- BlueZ 5.x - Linux Bluetooth stack
+
+## Development Workflow
+
+1. **Understanding the protocol:** Read BLE_PROTOCOL_v2.2.md sequence diagrams
+2. **Making changes:** Follow code patterns in existing driver implementations
+3. **Testing:** See TESTING.md for test execution
+4. **Contributing:** Follow guidelines in CONTRIBUTING.md
+
+## Key Files by Function
+
+**Discovery & Connection:**
+- `BLEInterface.py:_perform_discovery()` - Peer discovery and scoring
+- `BLEInterface.py:_connect_to_peer()` - Connection establishment
+
+**Data Flow:**
+- `BLEFragmentation.py` - Packet fragmentation/reassembly
+- `BLEInterface.py:handle_*_data()` - Data routing
+
+**Platform Integration:**
+- `linux_bluetooth_driver.py` - BlueZ interaction
+- `linux_bluetooth_driver.py:apply_bluez_*_patch()` - Platform workarounds
+
+## Quick Debugging
+
+**Check documentation first:**
+- Protocol issues → BLE_PROTOCOL_v2.2.md
+- Connection failures → BLE_PROTOCOL_v2.2.md § Troubleshooting
+- BlueZ quirks → BLE_PROTOCOL_v2.2.md § Platform-Specific Workarounds
+
+**Common issues are documented** in the protocol spec with solutions.