feat: Add split edit menu to single example

[cephalization]

splits.on.single.example.mov

Resolves #9839

---

Note

Integrates a splits management menu into the single example details dialog and queries datasetSplits to support it.

• Example Details Dialog (app/src/pages/example/ExampleDetailsDialog.tsx)
  • Integrates ExamplesSplitMenu into header (DialogTitleExtra) with size="S" for single example (selectedExampleIds set, empty selectedSplitIds).
  • Adds datasetSplits { id name color } to GraphQL query and builds examplesCache from example’s splits.
• GraphQL (app/src/pages/example/__generated__/ExampleDetailsDialogQuery.graphql.ts)
  • Updates query and types to include datasetSplits and adjusts selections accordingly.
• Examples Split Menu (app/src/pages/examples/ExamplesSplitMenu.tsx)
  • Adds optional size prop to button; updates heading copy for single-example context.
  • Documents single-example usage pattern (skip filter mode).

^{Written by Cursor Bugbot for commit 2457f74. This will update automatically on new commits. Configure here.}