refactor(doorbell-touch): add build harness with monitor agent and board-specific setup

.crushmemory

@@ -0,0 +1,32 @@
+# Doorbell Touch - Build Harness
+
+## Quick Commands
+```bash
+BOARD=esp32-32e-4 mise run compile   # Compile
+BOARD=esp32-32e-4 mise run upload    # Upload (auto-kills monitor)
+BOARD=esp32-32e-4 mise run monitor   # Start JSON monitor daemon
+BOARD=esp32-32e-4 mise run log-tail  # Watch colored logs
+BOARD=esp32-32e-4 mise run cmd COMMAND=dashboard  # Send command
+BOARD=esp32-32e-4 mise run state     # Show device state
+BOARD=esp32-32e-4 mise run install   # Install libs (shared + board)
+```
+
+## Files
+- `mise.toml` - Tasks (compile, upload, monitor, log-tail, cmd, state, install, clean)
+- `scripts/lockfile.sh` - Lockfile functions (acquire_lock, kill_locked)
+- `scripts/monitor-agent.py` - Serial monitor with JSON log + command FIFO
+- `scripts/install-shared.sh` - Shared Arduino libs (ArduinoJson, NTPClient)
+- `boards/{BOARD}/install.sh` - Board-specific vendor libs
+
+## Monitor Daemon
+- JSON log: `/tmp/doorbell-$BOARD.jsonl` - `{"ts":123.456,"line":"..."}`
+- State: `/tmp/doorbell-$BOARD-state.json` - `{"screen":"DASHBOARD",...}`
+- Cmd: `echo 'dashboard' > /tmp/doorbell-$BOARD-cmd.fifo`
+
+## Boards
+- esp32-32e (original 2.8" ILI9341)
+- esp32-32e-4 (4" ST7796)
+- esp32-s3-lcd-43 (4.3" S3 display)
+
+## Known Fixes
+- dashboard/off admin commands now reset inactivity timer (DoorbellLogic.cpp:234,240)