Remove build.sh from repo and update .gitignore

Dev convenience script should not be tracked.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -58,6 +58,7 @@ htmlcov/
 # Output test files.
 test_data/*.png
 
-#Project root scripts.
+# Dev scripts (local convenience scripts)
+build.sh
 rbld_containers.sh
 quick_web.sh