Populated (default, shown below): the evidenced demo fixture.
Empty / new site: reached via "Add new site" on the front page
(?new=1). All fields blank, Site Name required before Save is enabled:
Validation error: Save is blocked if Site Name is cleared on an existing record:
Loading: not shown — this static mockup has no network round-trip to simulate. Build stage should add a skeleton/placeholder state for the General tab's two columns while the record fetch is in flight, matching the loading pattern demonstrated on the Financial tab's state toggle.