Randomness 1.0.17

Follow-up to 1.0.16, clearing the last two warnings from the
automated review. No behaviour change.

Fixed

• vault.modify no longer needs an as any cast. The
  seedExampleGenerators flow narrowed a TAbstractFile | null
  to a TFile via duck-typing ("stat" in existing), which
  TypeScript can't follow — so the call site cast through any.
  Switched to instanceof TFile, which TypeScript's flow analysis
  recognises and narrows correctly. Same runtime behaviour;
  removes both the "unexpected any" and "unsafe argument"
  warnings.