🤖 test: reuse ssh test image for DockerRuntime fixture

Avoids an extra docker image build during runtime integration tests by reusing the existing mux-ssh-test image (bash+git already installed). This keeps CI integration runtime under the job timeout while still exercising DockerRuntime.

Author: ammar-agent

tests/runtime/test-fixtures/docker-fixture.ts

@@ -13,11 +13,9 @@ export interface DockerRuntimeTestConfig {
 }
 
 export async function startDockerRuntimeContainer(): Promise<DockerRuntimeTestConfig> {
-  // Build image used for DockerRuntime tests
-  const dockerfilePath = `${__dirname}/docker-runtime`;
-  const image = "mux-docker-runtime-test";
-
-  await execCommand("docker", ["build", "-t", image, dockerfilePath], { timeout: 60000 });
+  // Reuse the existing SSH runtime test image. It already includes bash + git,
+  // and avoids an extra docker build in CI.
+  const image = "mux-ssh-test";
 
   const containerName = `mux-docker-runtime-test-${crypto.randomBytes(8).toString("hex")}`;