docs: scaffold polisher-control foundation

host/README.md

@@ -0,0 +1,14 @@
+# Host Controller
+
+Python scaffold for the Raspberry Pi / host-side controller.
+
+Host responsibilities:
+- state machine orchestration;
+- geometric gate;
+- manual-mode UI integration;
+- serial/protocol session with Teensy;
+- controller-job validation;
+- telemetry capture;
+- logs, manifests, hashes, and `/data/status.json`.
+
+This package is intentionally small for now. Add real hardware adapters behind interfaces and keep state-machine/contract tests fast.