Enable testSendAndWaitThrowsOnTimeout in CI

- Enhanced CapiProxy.isAlive() to include HTTP health check
- When proxy crashes (e.g., due to no cached response), the HTTP check
  detects it and triggers automatic restart
- Removed @DisabledIfEnvironmentVariable annotation from timeout test
- All 80 tests now pass in CI mode

The upstream Node.js harness has a bug where it crashes on 'no cached
response' due to missing 'return' after exitWithNoMatchingRequestError.
This fix works around it by detecting the crashed proxy and restarting.

Author: brunoborges

src/test/java/com/github/copilot/sdk/CapiProxy.java

@@ -289,12 +289,34 @@ public String getProxyUrl() {
     }
 
     /**
-     * Checks if the proxy process is still alive.
+     * Checks if the proxy process is still alive and responsive. This does both a
+     * process alive check AND an HTTP health check.
      *
-     * @return true if the proxy is running, false otherwise
+     * @return true if the proxy is running and responsive, false otherwise
      */
     public boolean isAlive() {
-        return process != null && process.isAlive();
+        if (process == null || !process.isAlive()) {
+            return false;
+        }
+
+        // Also verify the proxy is responsive via HTTP
+        if (proxyUrl != null) {
+            try {
+                java.net.HttpURLConnection conn = (java.net.HttpURLConnection) new java.net.URL(proxyUrl + "/exchanges")
+                        .openConnection();
+                conn.setRequestMethod("GET");
+                conn.setConnectTimeout(1000);
+                conn.setReadTimeout(1000);
+                int responseCode = conn.getResponseCode();
+                conn.disconnect();
+                return responseCode == 200;
+            } catch (Exception e) {
+                // If HTTP check fails, the proxy is not responsive
+                return false;
+            }
+        }
+
+        return true;
     }
 
     /**

src/test/java/com/github/copilot/sdk/CopilotSessionTest.java

@@ -19,7 +19,6 @@
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.DisabledIfEnvironmentVariable;
 
 import com.github.copilot.sdk.events.AbstractSessionEvent;
 import com.github.copilot.sdk.events.AbortEvent;
@@ -487,12 +486,9 @@ void testCreateSessionWithCustomConfigDir() throws Exception {
         }
     }
 
-    // Skip in CI - this test validates client-side timeout behavior, not LLM
-    // responses.
-    // The test intentionally times out before receiving a response, so there's no
-    // snapshot to replay.
+    // This test validates client-side timeout behavior. The snapshot has no
+    // assistant response because the test expects timeout BEFORE completion.
     @Test
-    @DisabledIfEnvironmentVariable(named = "CI", matches = ".*")
     void testSendAndWaitThrowsOnTimeout() throws Exception {
         ctx.configureForTest("session", "sendandwait_throws_on_timeout");