Add project overview with session log

.claude-context/00-overview.md

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+# ps4-lego-bridge — Overview
+
+PS4 DualShock 4 controller driving a Johnny 5 (Short Circuit) LEGO MOC: seven
+motors across two LEGO Technic (Control+) hubs, plus two GPIO LED circuits.
+
+## Architecture in one paragraph
+Two ESP32 boards. **Board A** (`transmitter/`) runs Bluepad32 on the
+`esp32_bluepad32` 4.1.0 package, reads the pad over Bluetooth Classic, and
+streams checksummed ASCII frames over UART. **Board B** (`receiver/`) runs
+Legoino on plain `esp32` core 2.0.17 with NimBLE-Arduino 1.4.x, parses frames,
+and drives both hubs over BLE. Two boards because BTstack and NimBLE are both
+Bluetooth host stacks and cannot share one radio.
+
+## Branches
+- `main` — proven configuration: tank drive, power-controlled arms.
+- `johnny5-evolved` — current development: position-controlled arms on the
+  triggers, head on L1/R1 and d-pad, LED toggles, scan timeout.
+
+## Where to start
+- `README.md` — build guide, toolchain versions, wiring, power, gotchas.
+- `.claude-context/sessions/` — per-session notes.
+
+## Session Log
+- 2026-09-23 — PS4 Controller to Two LEGO Hubs — Johnny 5 Build — Pivoted from single to dual ESP32, got all seven motors working on main, then built position-controlled arms, LED toggles and scan retry on johnny5-evolved.
+
+---
+Created by: Jess Rogerson (yelling commands at Claude.AI)