fix(coding-agent/cli): qualified model IDs to avoid cross-provider collisions

- Updated PI native streaming requests to send model identifiers as provider-qualified keys.
- Updated the auth-gateway model registry to store `${provider}/${id}` first and retain legacy bare IDs as fallback keys.

packages/ai/src/providers/pi-native-client.ts

@@ -154,7 +154,7 @@ export function streamPiNative<TApi extends Api>(
 				typeof options?.apiKey === "string" ? options.apiKey : undefined,
 			);
 			const body = JSON.stringify({
-				modelId: model.id,
+				modelId: `${model.provider}/${model.id}`,
 				context,
 				options: buildWireOptions(options),
 				stream: true,

packages/coding-agent/src/cli/auth-gateway-cli.ts

@@ -175,8 +175,9 @@ async function runServe(flags: AuthGatewayCommandArgs["flags"]): Promise<void> {
 	for (const provider of getBundledProviders()) {
 		if (!providersWithCreds.has(provider)) continue;
 		for (const model of getBundledModels(provider as GeneratedProvider)) {
-			// First-write-wins so a canonical model id collisions across providers
-			// stick to the provider listed first by getBundledProviders.
+			// Always set the qualified key (no collision possible)
+			modelById.set(`${model.provider}/${model.id}`, model);
+			// Bare id as fallback for legacy clients (first-write-wins)
 			if (!modelById.has(model.id)) modelById.set(model.id, model);
 		}
 	}