chore: rename H7CAD to Open CAD Studio

Joining the OpenAEC Foundation (open-aec.com). Crate/struct become
OpenCADStudio, user-facing strings use the spaced "Open CAD Studio"
form, repo URLs point to HakanSeven12/open-cad-studio. Logo (window
icon + assets/logo.svg) redrawn with OCS initials. Drop examples/
binaries — unused.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

COMMANDS.md

@@ -1,6 +1,6 @@
-# H7CAD — Command Reference
+# Open CAD Studio — Command Reference
 
-Status of every standard CAD command in H7CAD:
+Status of every standard CAD command in Open CAD Studio:
 
 - ✅ **Implemented** — fully working
 - 🔶 **Partial** — command is accepted but logic is a stub