fix: enable enum description for API parameters

[Copilot]

Ticket: DX-1373

Enables individual descriptions for enum variants in OpenAPI output. Previously, enums generated from t.keyof() lost per-variant JSDoc comments during optimization.

Changes

• knownImports.ts: Preserve property comments when generating keyof enum variants
• optimize.ts: Skip consolidation for enum schemas with comments, maintaining oneOf structure
• comments.test.ts: Add test validating individual enum variant descriptions

Example

export const TransactionRequestState = t.keyof({
  /** Transaction is waiting for approval from authorized users */
  pendingApproval: 1,
  /** Transaction was canceled by the user */
  canceled: 1,
});

Now generates OpenAPI with individual descriptions:

{
  "oneOf": [
    {
      "type": "string",
      "enum": ["pendingApproval"],
      "description": "Transaction is waiting for approval from authorized users"
    },
    {
      "type": "string",
      "enum": ["canceled"],
      "description": "Transaction was canceled by the user"
    }
  ]
}

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