Separate Windows sandbox implementations from legacy setup modes (#45737)

## Why

`allowedWindowsSandboxImplementations` uses the legacy setup-mode type, which cannot represent `mxc`.

## What changed

- Introduce `WindowsSandboxImplementation` with `elevated`, `unelevated`, and `mxc` variants for configuration requirements, and update the generated schemas and TypeScript and Python types.
- Keep `WindowsSandboxSetupMode` limited to `elevated` and `unelevated`, and update the requirements mapping and its test assertions to use the new type.
- Document that clients selecting `mxc` skip the legacy setup and readiness APIs and use the standard `command/exec` streaming and process-control path.

GitOrigin-RevId: c926e853f0bbdb29d4b437866c284c1394a7ea13

sdk/python/src/openai_codex/generated/v2_all.py

@@ -6423,6 +6423,12 @@ class WebSearchToolConfig(BaseModel):
     location: WebSearchLocation | None = None
 
 
+class WindowsSandboxImplementation(Enum):
+    elevated = "elevated"
+    unelevated = "unelevated"
+    mxc = "mxc"
+
+
 class WindowsSandboxReadiness(Enum):
     ready = "ready"
     not_configured = "notConfigured"
@@ -11312,7 +11318,8 @@ class ConfigRequirements(BaseModel):
         list[WebSearchMode] | None, Field(alias="allowedWebSearchModes")
     ] = None
     allowed_windows_sandbox_implementations: Annotated[
-        list[WindowsSandboxSetupMode] | None, Field(alias="allowedWindowsSandboxImplementations")
+        list[WindowsSandboxImplementation] | None,
+        Field(alias="allowedWindowsSandboxImplementations"),
     ] = None
     auto_review: Annotated[AutoReviewRequirements | None, Field(alias="autoReview")] = None
     browser_use: Annotated[BrowserUseRequirements | None, Field(alias="browserUse")] = None