fix: emit stringish types for HTTP header parameters

Header parameters now emit \`${number}\` and 'true'|'false' literal types
instead of native number/boolean, matching how query and path parameters
already work.

HTTP headers are strings on the wire, and rest-client's Command<...>
defaults its CommandHeaders generic to Record<string, string>. A
generated header type containing a number-typed field could not satisfy
that constraint, breaking command construction at the call site.

The coerced valibot schema already accepts string|number on parse, so
runtime behaviour is unchanged — only the user-facing input type widens.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: maxholman

__tests__/__snapshots__/nullables.test.ts.snap

@@ -26,7 +26,7 @@ exports[`header parameters 1`] = `
 "export type UploadStatus = "pending" | "complete";
 export type UploadDataCommandHeader = {
         "content-type": "application/json" | "text/csv" | "application/xml";
-        "content-length": number;
+        "content-length": \`\${number}\`;
         "x-idempotency-key"?: string;
     };
 export type UploadDataCommandParams = {
@@ -135,7 +135,7 @@ export type ListFilesCommandQuery = {
         limit?: \`\${number}\` | undefined;
     };
 export type ListFilesCommandHeader = {
-        "x-rate-limit": number;
+        "x-rate-limit": \`\${number}\`;
     };
 export type ListFilesCommandInput = ListFilesCommandQuery;
 "

__tests__/fixtures/test1/types.ts

@@ -3,7 +3,7 @@
  *
  * WARN: Do not edit directly.
  *
- * Generated on 2026-05-09T08:13:13.582Z
+ * Generated on 2026-05-09T08:17:30.691Z
  *
  */
 import type { Jsonifiable, Jsonify } from "type-fest";
@@ -221,7 +221,7 @@ export type LongRunningOperation =
 	| LongRunningOperationSuccess;
 export type ImportBillingDataCommandHeader = {
 	"content-type": "application/json" | "text/csv" | "application/xml";
-	"content-length": number;
+	"content-length": `${number}`;
 	"x-idempotency-key"?: string;
 };
 type ImportBillingDataCommandBodyApplicationOctetStream = NonNullable<

lib/process-document.ts

@@ -549,10 +549,8 @@ export async function processOpenApiDocument(
 												name,
 												hp.schema,
 												{
-													// headers are strings on the wire but
-													// valibot parses them to native types
-													booleanAsStringish: false,
-													integerAsStringish: false,
+													booleanAsStringish: true,
+													integerAsStringish: true,
 												},
 											);