Summary

While looking into #1841 (a boolean-literal discriminant reportedly collapsing to a single value), I checked the current reflect.schema output and the metadata is correct — but our test suite doesn't actually pin that behavior. test_reflect_schema_constant only exercises a bare <true> literal; there is no coverage for <false> nor for a boolean-keyed discriminated union.

This adds that missing regression coverage so a future change can't silently collapse a union's false branch onto true (which would break discriminated-union narrowing) without a test going red.

What it checks

• a bare false literal reflects to a boolean constant with value false
• the discriminated union from Boolean literal discriminant collapses to single value in tagged unions #1841 keeps both false and true across its branch objects:

type U =
  | { ok: false; error: { code: string } }
  | { ok: true; code: string; data: { id: string } };

Test

• New case test_reflect_schema_boolean_literal_union follows the existing reflect.schema suite shape (one case per file, TestValidator).
• pnpm run build passes locally; the reflected output for the new case was verified to contain both branch values ([false, true]).

Refs #1841