Errors on the origins and migrate pages are §5's field error, not .error-note #5072

Intent: same pattern as #4807.

Done:

• [ ] src/web/pages/origins.ts (2) and migrate.ts (1) no longer write error-note
• [ ] a test for a refused connect or migrate finds the error in its field or at the form's head
• [ ] run test/web-origins.test.ts and the migrate tests
• [ ] the .error-note rule and §5d stay; another issue removes them