test: open channels from all implementations in one block

Add a channel opened by CLN and a second channel opened by the same
LDK node to block 503, which already has channel opens from LDK and
lnd. This checks that funding transactions from all four
implementations land at their index in one block, and covers LDK's
one-at-a-time channel opens per node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: pinheadmz

test/data/ln_mixed/network.yaml

@@ -56,6 +56,13 @@ nodes:
           target: tank-0003-ln
           capacity: 100000
           push_amt: 50000
+        # Block 503 has channel opens from all four implementations
+        - id:
+            block: 503
+            index: 3
+          target: tank-0000-ln
+          capacity: 100000
+          push_amt: 50000
 
   - name: tank-0003
     addnode:
@@ -95,6 +102,13 @@ nodes:
           target: tank-0002-ln
           capacity: 100000
           push_amt: 50000
+        # Opened after the first one, which LDK's wallet must have seen first
+        - id:
+            block: 503
+            index: 4
+          target: tank-0003-ln
+          capacity: 100000
+          push_amt: 50000
 
   - name: tank-0006
     addnode:

test/ln_mixed_test.py

@@ -28,6 +28,8 @@
     (502, 1, "tank-0003-ln", "tank-0000-ln"),
     (503, 1, "tank-0005-ln", "tank-0002-ln"),
     (503, 2, "tank-0000-ln", "tank-0006-ln"),
+    (503, 3, "tank-0002-ln", "tank-0000-ln"),
+    (503, 4, "tank-0005-ln", "tank-0003-ln"),
 ]