feat(network): SSE optimization for local LLM streaming (#31 #32 #33) (#26)

Addresses three critical network issues for LLM streaming performance:

**#33 Disable proxy buffering for SSE**
- Add X-Accel-Buffering: no header to response
- Tells nginx/Ingress to stream events immediately instead of buffering

**#32 HTTP/2 multiplexing for concurrent streams**
- Enable HTTP/2 in server config via http2.ConfigureServer()
- Increase MaxConnsPerHost to 10 for better concurrency
- Allows multiple concurrent LLM requests without blocking

**#31 TCP backpressure for streaming LLM responses**
- Set TCP_NODELAY on dialer to disable Nagle's algorithm
- Reduces latency by sending small packets immediately
- Critical for low TTFT (time-to-first-token) under load

**Tests added:**
- TestTCPBackpressure: Verifies TCP backpressure handling with slow client
- TestConcurrentSSEStreams: Confirms HTTP/2 multiplexing works correctly

---------

Co-authored-by: poison <[email protected]>
Reviewed-on: #26
Co-authored-by: poimen <[email protected]>

k8s/tekton/scripts/integration-test.sh

@@ -76,10 +76,56 @@ echo "▸ SQS service"
 assert "sqs/list-queues" 401 \
   -X GET -H "X-Service: sqs" -H "X-Resource: list-queues" "${GW}/"
 
-# ── Workflow (gRPC needs content-type → 400) ──
+# ── Workflow visibility (namespace pass-down) ──
 echo "▸ Workflow service"
-assert "workflow/list (no grpc content-type → 400)" 400 \
-  -X GET -H "X-Service: workflow" -H "X-Resource: list" "${GW}/"
+
+# Test 1: List workflows in poimen-harness namespace (should see 4 terminated workflows)
+echo "  Testing workflow visibility in poimen-harness namespace..."
+WF_LIST=$(curl -s -X POST \
+  -H "X-Service: workflow" \
+  -H "X-Resource: list" \
+  -H "Content-Type: application/json" \
+  -d '{"namespace": "poimen-harness"}' \
+  "${GW}/" 2>/dev/null || echo '{}')
+
+# Check if response contains workflows
+if echo "$WF_LIST" | grep -q '"executions"'; then
+  echo "  ✓ Workflow list returned (poimen-harness namespace)"
+  PASS=$((PASS + 1))
+else
+  echo "  ✗ Workflow list failed to return executions"
+  FAIL=$((FAIL + 1))
+fi
+TOTAL=$((TOTAL + 1))
+
+# Test 2: Verify we can query terminated workflows
+echo "  Testing terminated workflow visibility..."
+if echo "$WF_LIST" | grep -q '"Completed\|"status"'; then
+  echo "  ✓ Found completed/terminated workflows in response"
+  PASS=$((PASS + 1))
+else
+  echo "  ⚠ No terminated workflows found in response (may be empty namespace)"
+  # Don't fail if namespace is empty - just note it
+fi
+TOTAL=$((TOTAL + 1))
+
+# Test 3: Verify namespace is required (missing namespace → 400)
+echo "  Testing namespace validation..."
+NO_NS=$(curl -s -w '%{http_code}' -X POST \
+  -H "X-Service: workflow" \
+  -H "X-Resource: list" \
+  -H "Content-Type: application/json" \
+  -d '{}' \
+  "${GW}/" 2>/dev/null || echo "000")
+
+if [ "$NO_NS" = "400" ]; then
+  echo "  ✓ Correctly rejected list without namespace (400)"
+  PASS=$((PASS + 1))
+else
+  echo "  ✗ Expected 400 for missing namespace, got $NO_NS"
+  FAIL=$((FAIL + 1))
+fi
+TOTAL=$((TOTAL + 1))
 
 echo ""
 echo "═══ Results: ${PASS}/${TOTAL} passed, ${FAIL} failed ═══"