Clear the browser selection when Cmd/Ctrl + Click or Shift + Click starts a multiselection

[Copilot]

Running Define Term from the Command Universe on a Cmd + Click multiselection rendered a faux caret on every selected thought.

Cmd/Ctrl + Click and Shift + Click were the only multiselect entry points that left the caret in the clicked thought. isMultiEditing reads that stale caret as an edited multiselection (Clear Thought), so when the Command Universe restored the selection it saved on open, it re-focused the editable and the faux carets appeared. Define Term is incidental — dismissing the palette with Escape produces the same result, and executing the command directly produces none.

Changes

• Thought.tsx — handleMultiselect clears the browser selection before toggling or extending the multicursors, as selectAll and cursorUp/cursorDown already do. The check runs before the dispatch, since afterwards the clicked thought is itself a multicursor and a caret still in it would read as multi edit mode. It is skipped while the multiselection is being edited, where clearing the caret would blur the thought and exit the cleared state.
• multiselect.ts — Puppeteer regression test asserting no faux-caret-multicursor after Define Term runs on a Cmd + Click multiselection, plus an arrange-only acknowledgeAiDisclosure helper (the disclosure modal otherwise takes focus and masks the bug).
• docs/cursor-and-caret.md — the click entry points now appear in the list that upholds the caret invariant, and the Command Universe is named alongside Copy Cursor as a surface that restores a saved selection.

dispatch((dispatch, getState) => {
  if (!isMultiEditing(getState())) selection.clear()
  dispatch(mouseEvent.shiftKey ? selectBetween({ path }) : toggleMulticursor({ path }))
})

Side effect worth noting in review: Backspace and Escape on a Cmd + Click multiselection previously deferred to the browser because isMultiEditing was wrongly true, and now take the multiselect path.

• Fixes [Desktop] Faux Caret is activated when user runs Define Term on manual selection with Cmd+Click #5405

[BayuAri]

Confirmed fixed.
Faux caret does not activate on Define Term after manual selection.
This also fixes #5468

[raineorshine]

Thanks!