every control writes itself

The Save button is gone, and so is the SaveTarget context that announced it.
Every screen here is a preview of the thing being edited, so a change is already
visible before it is written — a button then asks somebody to confirm what they
can see.

useAutosave debounces a burst into one request. It takes the unsaved state as a
string rather than a flag, so a failed save is not retried on the next render,
and it flushes on unmount so a section change loses nothing.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/sections/HomePanel.tsx

@@ -7,7 +7,7 @@ import { readableError } from '../errors';
 import { useFlash } from '../useFlash';
 import { RichText } from '../RichText';
 import { MediaPicker } from '../MediaPicker';
-import { useSaveTarget } from '../SaveTarget';
+import { useAutosave } from '../useAutosave';
 
 /**
  * The Home page: a hero, an intro, and an ordered gallery.
@@ -129,7 +129,7 @@ export const HomePanel = () => {
 
   const save = () => send('save', () => clientRef.current.patch<{ data: Home }>('/fofos-admin/home', edited));
 
-  useSaveTarget(dirty, busy !== null, save);
+  useAutosave(dirty ? 'dirty' : null, busy !== null, save);