Dev setup Windows-first + LF-pin shell scripts

PowerShell-first onboarding (most devs are on VS Code/Windows), a
Windows variant for the VS Code check task, and a .gitattributes rule
keeping shell scripts LF so Windows checkouts do not corrupt them.

.vscode/tasks.json

@@ -36,6 +36,9 @@
       "label": "Check: naming + tests + build",
       "type": "shell",
       "command": "bash scripts/check-naming-and-style.sh && venv/bin/python -m pytest tests/ -q && cd frontend && npx vitest run && npm run build",
+      "windows": {
+        "command": "bash scripts/check-naming-and-style.sh && venv\\Scripts\\python -m pytest tests/ -q && cd frontend && npx vitest run && npm run build"
+      },
       "options": { "cwd": "${workspaceFolder}" },
       "problemMatcher": []
     }