Add browser-based AirCube monitor (Web Serial) for Chromebooks

[craigpfeifer]

Summary

Adds scripts/aircube_webapp.html, a browser-based replacement for the aircube_app.py desktop app that works on Chromebooks (and any Chrome/Edge browser).

The PyQt6 desktop app cannot run on a Chromebook:

• pyserial sees nothing -- the Crostini (termina) VM kernel has no cdc-acm module, so no /dev/ttyACM* is ever created.
• pyusb can open the device but not read -- the ESP32-H2 USB Serial/JTAG gates TX until the host marks the port "connected", and the required SET_CONTROL_LINE_STATE (class interface-OUT) control transfer times out through ChromeOS/Crostini's USB passthrough.

The web app reads over the Web Serial API instead (through the ChromeOS host's cdc-acm driver), using the DTR=0 RTS=1 handshake the ESP32-H2 USB Serial/JTAG requires. Note: DTR=1 resets/halts the chip, which was the root cause of an initially silent stream.

What's included

• aircube_webapp.html -- full app: live value cards (with AQI color bands), C/F toggle, three scrolling charts (canvas, no external libs), CSV logging (session download + File System Access streaming), field-definition tooltips, and device controls (get_config, set_intensity, set_readout_period, history dump). Apache 2.0 header.
• WEBAPP_README.md -- usage, the full Chromebook investigation, serial protocol reference, and troubleshooting.
• Diagnostic artifacts referenced by the README: webserial_aircube_test.html, webusb_aircube_test.html, test_serial_discovery.py, test_pyusb_discovery.py.

Testing

Verified live streaming, charts, C/F toggle, CSV download, and get_config/set_intensity round-trips against an AirCube on a Chromebook over http://localhost.

🤖 Generated with Claude Code