feat(stream-check): support OpenClaw openai-completions protocol

Phase 1 of extending stream health check to OpenCode/OpenClaw apps.

- Add early-dispatch path for OpenCode/OpenClaw in check_once so they
  bypass the adapter layer (which only knows Claude/Codex/Gemini
  settings_config shapes).
- Introduce check_openclaw_stream dispatcher that reads the `api` field
  from settings_config and routes to the existing check_claude_stream
  with api_format="openai_chat" for "openai-completions". Other
  protocols return localized errors to be lit up in phases 2 and 4.
- Extract build_stream_check_result helper to avoid duplicating the
  StreamCheckResult construction logic between the two code paths.
- Unblock the test button for OpenClaw providers in ProviderList.tsx.

OpenCode still returns the "not yet supported" error; it will be
enabled in phase 3.

src/components/providers/ProviderList.tsx

@@ -348,11 +348,7 @@ export function ProviderList({
                 onConfigureUsage={onConfigureUsage}
                 onOpenWebsite={onOpenWebsite}
                 onOpenTerminal={onOpenTerminal}
-                onTest={
-                  appId !== "opencode" && appId !== "openclaw"
-                    ? handleTest
-                    : undefined
-                }
+                onTest={appId !== "opencode" ? handleTest : undefined}
                 isTesting={isChecking(provider.id)}
                 isProxyRunning={isProxyRunning}
                 isProxyTakeover={isProxyTakeover}