Add modelReasoningEffort option to TypeScript SDK (#6237)

## Summary
- Adds `ModelReasoningEffort` type to TypeScript SDK with values:
`minimal`, `low`, `medium`, `high`
- Adds `modelReasoningEffort` option to `ThreadOptions`
- Forwards the option to the codex CLI via `--config
model_reasoning_effort="<value>"`
- Includes test coverage for the new option

## Changes
- `sdk/typescript/src/threadOptions.ts`: Define `ModelReasoningEffort`
type and add to `ThreadOptions`
- `sdk/typescript/src/index.ts`: Export `ModelReasoningEffort` type
- `sdk/typescript/src/exec.ts`: Forward `modelReasoningEffort` to CLI as
config flag
- `sdk/typescript/src/thread.ts`: Pass option through to exec (+ debug
logging)
- `sdk/typescript/tests/run.test.ts`: Add test for
`modelReasoningEffort` flag forwarding

---------

Co-authored-by: Eric Traut <etraut@openai.com>

sdk/typescript/tests/run.test.ts

@@ -223,6 +223,37 @@ describe("Codex", () => {
     }
   });
 
+  it("passes modelReasoningEffort to exec", async () => {
+    const { url, close } = await startResponsesTestProxy({
+      statusCode: 200,
+      responseBodies: [
+        sse(
+          responseStarted("response_1"),
+          assistantMessage("Reasoning effort applied", "item_1"),
+          responseCompleted("response_1"),
+        ),
+      ],
+    });
+
+    const { args: spawnArgs, restore } = codexExecSpy();
+
+    try {
+      const client = new Codex({ codexPathOverride: codexExecPath, baseUrl: url, apiKey: "test" });
+
+      const thread = client.startThread({
+        modelReasoningEffort: "high",
+      });
+      await thread.run("apply reasoning effort");
+
+      const commandArgs = spawnArgs[0];
+      expect(commandArgs).toBeDefined();
+      expectPair(commandArgs, ["--config", 'model_reasoning_effort="high"']);
+    } finally {
+      restore();
+      await close();
+    }
+  });
+
   it("writes output schema to a temporary file and forwards it", async () => {
     const { url, close, requests } = await startResponsesTestProxy({
       statusCode: 200,