fix(optimizer): simplify redundant intersections in allOf schemas

[privatenumber]

Problem

When a JSON Schema uses allOf with $ref that overlap, the generated TypeScript contains redundant intersections and duplicate properties.

Example from the tsconfig.json schema:

export type CompilerOptions = {
  types?: (string | null)[] | null;
  target?: string | null;
  [k: string]: unknown;
} & ({
  types?: (string | null)[] | null;  // Duplicate
  target?: string | null;             // Duplicate
  [k: string]: unknown;
} | null);

This happens when:

1. A schema definition is $ref’d multiple times
2. One $ref wraps the base in an allOf with extra constraints
3. The parser generates multiple AST nodes with the same name but different shapes

Before

export type CompilerOptions = {...} & ({...} | null);

Changes

1. Optimizer (optimizer.ts)

   • Simplifies A & (A | null) → A | null
   • Handles both (A & (A | null)) and (A | null) & A
   • Deduplicates intersections like A & B & A & B → A & B

2. Generator (generator.ts)

   • Tracks generated type names with a Set
   • Skips duplicate export type declarations

After

export type CompilerOptions = {...} | null;