feat(stream-check): support OpenCode via npm package mapping

Phase 3: implement stream check for OpenCode providers by mapping the
`settings_config.npm` (AI SDK package name) to the corresponding API
protocol and delegating to the existing stream checkers.

Package mapping:
- @ai-sdk/openai-compatible → openai_chat
- @ai-sdk/openai            → openai_responses
- @ai-sdk/anthropic         → anthropic (ClaudeAuth strategy)
- @ai-sdk/google            → gemini (Google strategy)
- @ai-sdk/amazon-bedrock    → not supported (phase 4 message polish)

Note: OpenCode nests baseURL/apiKey under `settings_config.options`
(different from OpenClaw's root-level fields) and uses `baseURL` with
a capital L. Three new extractors (base_url / api_key / npm) encode
these shape differences so check_opencode_stream stays symmetric with
check_openclaw_stream.

Frontend: drop the remaining `appId !== "opencode"` filter in
ProviderList.tsx — both apps can now test providers.

src/components/providers/ProviderList.tsx

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