feat: add library-based ts-to-zod schema generation

Replace CLI-based ts-to-zod usage with library-based generation that:

1. **@description injection during fetch**: The fetch-spec-types.ts script
   now automatically extracts the first paragraph of each JSDoc comment
   and adds it as a @description tag. This enables ts-to-zod to generate
   .describe() calls in the Zod schemas.

2. **Library-based generation**: New generate-schemas.ts script uses
   ts-to-zod as a library with configuration options:
   - keepComments: true - preserves JSDoc comments
   - skipParseJSDoc: false - parses @description tags
   - getSchemaName: camelCase naming for backwards compatibility

3. **Post-processing**: Robust brace-counting algorithm to replace
   z.record().and(z.object()) with z.looseObject() for index signatures.

4. **Integration tests**: Auto-generated tests verify that Zod schemas
   match their corresponding TypeScript types at compile time.

Generated 145 Zod schemas with full descriptions in src/generated/.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ochafik