docs: Complete v0.1 documentation sprint

- Add build & flash workflow (docs/INSTALL.md)
- Add CSI config reference and firmware comparison (docs/USAGE.md)
- Add quick reference cheatsheet (docs/CHEATSHEET.md)
- Add dependencies.lock to .gitignore (env-specific)
- Update TASKS.md with completed items and build notes
- Verified firmware builds on ESP-IDF v6.1.0 / aarch64

docs/CHEATSHEET.md

@@ -0,0 +1,95 @@
+# Cheatsheet
+
+## Environment Setup
+
+```bash
+source ~/esp/esp-idf/export.sh          # Activate ESP-IDF (every shell)
+```
+
+## Build & Flash
+
+```bash
+cd ~/git/esp32-hacking/get-started/csi_recv_router
+
+idf.py set-target esp32                 # Set chip target
+idf.py menuconfig                       # Configure WiFi/UDP settings
+idf.py build                            # Compile firmware
+idf.py -p /dev/ttyUSB0 flash            # Flash to device
+idf.py -p /dev/ttyUSB0 monitor          # Serial monitor (Ctrl+] to exit)
+idf.py -p /dev/ttyUSB0 flash monitor    # Flash + monitor combined
+idf.py fullclean                        # Clean build directory
+idf.py reconfigure                      # Re-fetch managed components
+
+# IDF v6.1 workaround (after clean/reconfigure)
+ln -s 6.0 managed_components/espressif__esp_csi_gain_ctrl/6.1
+```
+
+## Deployed Sensors
+
+| Name | IP | Location |
+|------|-----|----------|
+| muddy-storm | 192.168.129.29 | Living Room |
+| amber-maple | 192.168.129.30 | Office |
+| hollow-acorn | 192.168.129.31 | Kitchen |
+
+**Target:** `192.168.129.11:5500` (Pi)
+
+## Test CSI Reception
+
+```bash
+nc -lu 5500                             # Listen for CSI packets
+socat UDP-RECV:5500 STDOUT              # Alternative listener
+nc -lu 5500 | head -1                   # See one packet
+nc -lu 5500 | wc -l                     # Count packets/sec (Ctrl+C)
+```
+
+## Firmware Variants
+
+| Firmware | Dir | Output | Needs |
+|----------|-----|--------|-------|
+| csi_recv_router | `get-started/csi_recv_router/` | UDP | WiFi router |
+| csi_recv | `get-started/csi_recv/` | Serial | csi_send device |
+| csi_send | `get-started/csi_send/` | N/A | csi_recv device |
+
+## Key Config (menuconfig)
+
+| Path | Setting |
+|------|---------|
+| Example Connection Configuration → SSID | WiFi network name |
+| Example Connection Configuration → Password | WiFi password |
+| CSI UDP Configuration → IP | `192.168.129.11` |
+| CSI UDP Configuration → Port | `5500` |
+
+## CSI Data Format
+
+```
+CSI_DATA,seq,mac,rssi,rate,sig_mode,mcs,cwb,smoothing,not_sounding,
+aggregation,stbc,fec_coding,sgi,noise_floor,ampdu_cnt,channel,
+secondary_channel,timestamp,ant,sig_len,rx_state,len,first_word,"[I,Q,...]"
+```
+
+## Source Paths
+
+| File | Purpose |
+|------|---------|
+| `get-started/csi_recv_router/main/app_main.c` | Main firmware source |
+| `get-started/csi_recv_router/main/Kconfig.projbuild` | UDP target config |
+| `get-started/csi_recv_router/sdkconfig.defaults` | SDK defaults |
+| `get-started/csi_recv_router/main/idf_component.yml` | Dependencies |
+| `get-started/csi_recv_router/CMakeLists.txt` | Build config |
+
+## ESP-IDF Paths
+
+| Path | Contents |
+|------|----------|
+| `~/esp/esp-idf/` | ESP-IDF v6.1.0 |
+| `~/esp/esp-csi/` | Original esp-csi examples |
+| `~/.espressif/tools/` | Xtensa toolchain |
+
+## USB Serial
+
+```bash
+ls /dev/ttyUSB* /dev/ttyACM*            # Find connected devices
+dmesg | tail                             # Check USB detection
+sudo usermod -aG dialout $USER           # Fix permissions (re-login)
+```