Software: pattern player, web page with a design library, GRBL tools

- python3 -m sandtable web: local web page to play designs from a library of
  27 built-in patterns, upload .thr or .svg, pause/skip/stop, jog and calibrate.
  Reconnects by itself when the USB cable comes back.
- Plays .thr files and built-in generators with an erase spiral between them,
  constant ball speed, host-side homing on stock GRBL 1.1 (Uno + CNC shield),
  FluidNC for the ESP32 board.
- Home switch guard: patterns never press the switch, so a press means lost
  steps and stops the machine at once with an alert.
- lineart.py turns SVG line drawings into one continuous path.
- Tests against a GRBL simulator.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

software/tests/demo_web.py

@@ -0,0 +1,18 @@
+"""Try the web page without the table: the real design library, driven against the GRBL simulator.
+Run from the software folder:  python3 tests/demo_web.py   then open http://127.0.0.1:8766"""
+import os
+import sys
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..'))
+sys.path.insert(0, os.path.dirname(__file__))
+
+from sandtable import config
+from sandtable.grbl import Controller
+from sandtable.web import serve
+from fakegrbl import FakeGrbl
+
+if __name__ == '__main__':
+    fake = FakeGrbl(speedup=float(os.environ.get('SPEEDUP', '30')), carriage_mm=40.0)
+    c = Controller(fake, 'grbl', log=lambda *a: None)
+    c.wake(wait=0.3)
+    serve(c, config.load(), port=int(os.environ.get('PORT', '8766')), open_browser='--no-browser' not in sys.argv)