feat(core): add formatType config for custom string format types

[chrisahardie]

Partially solves #1939

Summary

Adds override.formatType — a config that maps any OpenAPI string format (e.g. date, date-time, uuid, email) to a custom TypeScript type, with integrated support across Zod schemas, Effect schemas, faker mocks, and factory defaults.

Motivation

Users working with Temporal API, dayjs, branded types, or domain-specific formats have no way to override the generated type for string formats beyond the binary useDates flag. This feature generalizes type mapping to any format string, with full control over imports, Zod validation, mock generation, and factory defaults.

Config shape

override: {
  formatType: {
    'date-time': {
      type: 'Dayjs',
      import: { name: 'Dayjs', importPath: 'dayjs' },
      zod: {
        transform: 'dayjs',
        transformImport: { name: 'dayjs', importPath: 'dayjs', default: true },
      },
      mock: 'dayjs(faker.date.past())',
      mockImport: { name: 'dayjs', importPath: 'dayjs', default: true },
    },
    date: { type: 'Temporal.PlainDate' },
    uuid: { type: 'UUID', import: { name: 'UUID', importPath: '@company/types' } },
  },
}

What's NOT in scope

Runtime response deserialization and request body serialization are deliberately excluded. These are orthogonal concerns being addressed separately (see #1939).

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	dayjs@​1.11.21

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