feat(explorer): add ChristenUnie colour alias and CURRENT_PARLIAMENT_PARTIES constant

docs/superpowers/plans/2026-03-24-svd-tab-redesign.md

explorer.py

@@ -49,6 +49,7 @@ PARTY_COLOURS: Dict[str, str] = {
     "DENK": "#00897B",
     "50PLUS": "#7E57C2",
     "Volt": "#572AB7",
+    "ChristenUnie": "#0288D1",
     "Unknown": "#9E9E9E",
 }
 
@@ -69,6 +70,29 @@ KNOWN_MAJOR_PARTIES = [
 ]
 
 
+# Parties currently seated in the Tweede Kamer (2023 election cycle).
+# Deze zijn de entity_ids zoals opgeslagen in svd_vectors voor window='2025'.
+CURRENT_PARLIAMENT_PARTIES: frozenset[str] = frozenset(
+    {
+        "PVV",
+        "VVD",
+        "NSC",
+        "BBB",
+        "D66",
+        "GroenLinks-PvdA",
+        "CDA",
+        "SP",
+        "ChristenUnie",
+        "SGP",
+        "Volt",
+        "DENK",
+        "PvdD",
+        "JA21",
+        "FVD",
+    }
+)
+
+
 # ---------------------------------------------------------------------------
 # Cached loaders
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