Slate React repair-induced selectionchange must stay model-owned

Problem

After Slate handles a destructive browser edit as model-owned, the DOM repair it schedules can itself trigger selectionchange. If that repair-induced selectionchange re-enters the pipeline as dom-current, a delayed browser selection can reopen DOM authority after the model mutation is already correct.

Symptoms

• Repeated Alt+Backspace in /examples/richtext could produce screenshot-class drift where visual text/caret state no longer matched the intended model lane.
• Headless Playwright did not always reproduce the exact visual split, but the kernel trace showed the authority leak: repair-induced selectionchange events reported selectionSource: dom-current.
• Follow-up typing was the necessary proof: final text alone could look correct while the next input still used stale selection authority.

What Didn't Work

• Reproducing only the screenshot was not reliable enough. The deterministic RED was the trace invariant: repair-induced selection changes after model-owned destructive edits must remain model-owned.
• Blocking all native selectionchange imports while model selection was preferred was too blunt. It fixed the word-delete row but broke legitimate DOM selection import for toolbar commands and paste.
• Model-only assertions missed the bug class because the model mutation could be correct while the visible browser caret and next-event selection source were wrong.

Solution

Treat destructive model-owned beforeinput repairs as model-owned all the way through the repair-induced selectionchange event:

repair: {
  focus: true,
  kind: 'repair-caret',
  selectionSourceTransition: {
    preferModelSelection: true,
    reason: 'model-command',
    selectionSource: 'model-owned',
  },
}

Then, when selectionchange is known to be repair-induced, canonicalize the editable selection preference before tracing or importing:

if (selectionChangeOrigin === 'repair-induced') {
  setEditableModelSelectionPreference({
    preferModelSelection: true,
    selectionSource: 'model-owned',
  })
}

Finally, clear only the transient repair origin after that repair event. Keep model preference/source active, but allow later explicit user DOM selection to import normally.

Why This Works

The repair event is not a fresh user intent. It is a consequence of a model-owned mutation. Letting it report as dom-current creates two competing selection authorities inside one native action.

The narrow rule keeps the right split:

• repair-induced selectionchange stays model-owned
• later real user selection can still import from DOM
• toolbar and paste flows are not broken by a global model-preference guard

Prevention

• Add browser rows for destructive native edits that assert model text, visible DOM text, DOM selection containment, follow-up typing, and trace source.
• Trace repair-induced selectionchange separately from native user selectionchange.
• Do not accept broad "ignore DOM selection" fixes unless toolbar selection and paste rows stay green.
• Build generated gauntlets around authority invariants, not only final text.

Related Issues

• Slate React model-owned input must ignore stale DOM target ranges
• Slate React keydown must import DOM selection before model-owned navigation
• Slate React model-owned insert must repair the DOM caret