fix(test): update Forward-compat / Protocol-version / Backpressure ITs

- ForwardCompatIT: send a valid ExecutionChunk envelope with extra
  unknown fields instead of a bare {futureField}. Was being parsed into
  an empty/degenerate chunk and rejected with 400.
- ProtocolVersionIT.requestWithCorrectProtocolVersionPassesInterceptor:
  same shape fix — minimal valid chunk so the controller's 400 is not
  an ambiguous signal for interceptor-passthrough.
- BackpressureIT:
  * TestPropertySource keys were "ingestion.*" but IngestionConfig is
    bound under "cameleer.server.ingestion.*" — overrides were ignored
    and the buffer stayed at its default 50_000, so the 503 overflow
    branch was unreachable. Corrected the keys.
  * MetricsFlushScheduler's @Scheduled uses a *different* key again
    ("ingestion.flush-interval-ms"), so we override that separately to
    stop the default 1s flush from draining the buffer mid-test.
  * executionIngestion_isSynchronous_returnsAccepted now uses the
    chunked envelope format.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/test/java/com/cameleer/server/app/controller/BackpressureIT.java

@@ -22,9 +22,17 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Only the metrics pipeline still uses a write buffer with backpressure.
  */
 @TestPropertySource(properties = {
-        "ingestion.buffer-capacity=5",
+        // Property keys must match the IngestionConfig @ConfigurationProperties
-        "ingestion.batch-size=5",
+        // prefix (cameleer.server.ingestion) exactly — the old "ingestion.*"
-        "ingestion.flush-interval-ms=60000"  // 60s -- effectively no flush during test
+        // form was silently ignored and the metrics buffer stayed at its
+        // default of 50_000, which made the 503 overflow scenario unreachable.
+        "cameleer.server.ingestion.buffercapacity=5",
+        "cameleer.server.ingestion.batchsize=5",
+        "cameleer.server.ingestion.flushintervalms=60000",
+        // MetricsFlushScheduler's @Scheduled reads ingestion.flush-interval-ms
+        // (a separate key) — override both so the test doesn't race against
+        // the default 1s flush during the fill-then-overflow scenario.
+        "ingestion.flush-interval-ms=60000"
 })
 class BackpressureIT extends AbstractPostgresIT {
 
@@ -81,7 +89,19 @@ class BackpressureIT extends AbstractPostgresIT {
     @Test
     void executionIngestion_isSynchronous_returnsAccepted() {
         String json = """
-                {"routeId":"bp-sync","exchangeId":"bp-sync-e","status":"COMPLETED","startTime":"2026-03-11T10:00:00Z","durationMs":100,"processors":[]}
+                {
+                  "exchangeId": "bp-sync-e",
+                  "applicationId": "test-group",
+                  "instanceId": "test-agent-backpressure-it",
+                  "routeId": "bp-sync",
+                  "status": "COMPLETED",
+                  "startTime": "2026-03-11T10:00:00Z",
+                  "endTime": "2026-03-11T10:00:00.100Z",
+                  "durationMs": 100,
+                  "chunkSeq": 0,
+                  "final": true,
+                  "processors": []
+                }
                 """;
 
         ResponseEntity<String> response = restTemplate.postForEntity(

cameleer-server-app/src/test/java/com/cameleer/server/app/controller/ForwardCompatIT.java

@@ -33,10 +33,26 @@ class ForwardCompatIT extends AbstractPostgresIT {
 
     @Test
     void unknownFieldsInRequestBodyDoNotCauseError() {
+        // Valid ExecutionChunk plus extra fields a future agent version
+        // might send. Jackson is configured with FAIL_ON_UNKNOWN_PROPERTIES
+        // = false on ChunkIngestionController, so the extras must be ignored
+        // and the envelope accepted with 202.
         String jsonWithUnknownFields = """
                 {
-                    "futureField": "value",
+                  "exchangeId": "fwd-compat-1",
-                    "anotherUnknown": 42
+                  "applicationId": "test-group",
+                  "instanceId": "test-agent-forward-compat-it",
+                  "routeId": "fwd-compat-route",
+                  "status": "COMPLETED",
+                  "startTime": "2026-03-11T10:00:00Z",
+                  "endTime": "2026-03-11T10:00:01Z",
+                  "durationMs": 1000,
+                  "chunkSeq": 0,
+                  "final": true,
+                  "processors": [],
+                  "futureField": "value",
+                  "anotherUnknown": 42,
+                  "someNested": {"key": "v"}
                 }
                 """;
 

cameleer-server-app/src/test/java/com/cameleer/server/app/interceptor/ProtocolVersionIT.java

@@ -65,7 +65,26 @@ class ProtocolVersionIT extends AbstractPostgresIT {
         headers.setContentType(MediaType.APPLICATION_JSON);
         headers.set("Authorization", "Bearer " + jwt);
         headers.set("X-Cameleer-Protocol-Version", "1");
-        var entity = new HttpEntity<>("{}", headers);
+        // Minimal valid ExecutionChunk envelope so the controller can accept
+        // it; the prior {} body was treated by the chunk pipeline as an empty
+        // envelope and rejected with 400, which made the interceptor-passed
+        // signal ambiguous.
+        String chunk = """
+                {
+                  "exchangeId": "protocol-version-1",
+                  "applicationId": "test-group",
+                  "instanceId": "test-agent-protocol-it",
+                  "routeId": "protocol-version-route",
+                  "status": "COMPLETED",
+                  "startTime": "2026-03-11T10:00:00Z",
+                  "endTime": "2026-03-11T10:00:01Z",
+                  "durationMs": 1,
+                  "chunkSeq": 0,
+                  "final": true,
+                  "processors": []
+                }
+                """;
+        var entity = new HttpEntity<>(chunk, headers);
 
         var response = restTemplate.exchange(
                 "/api/v1/data/executions", HttpMethod.POST, entity, String.class);