fix: quiz seed from motions with actual individual MP votes

Root causes:
- Seed selection sorted by controversy_score across all 28k motions, but
  only 282 have individual MP vote records. Top controversial motions only
  have party-level votes, so match_mps_for_votes always returned empty.
- global_db singleton was used for match/discriminate instead of the db_path
  passed to the tab builder.

Fixes:
- Add MotionDatabase.get_motions_with_individual_votes(k) which queries
  motions with comma-formatted mp_name votes, ordered by controversy_score
- Replace broken seed logic in build_mp_quiz_tab with this new method
- Replace global_db usages with a local MotionDatabase(db_path) instance
- Guard against motion IDs present in votes but absent from motions DataFrame

database.py

@@ -657,6 +657,40 @@ class MotionDatabase:
 
         return sorted(results, key=lambda x: x["agreement_percentage"], reverse=True)
 
+    def get_motions_with_individual_votes(self, k: int = 20) -> List[int]:
+        """Return up to k motion IDs that have individual MP vote records.
+
+        Selects motions where at least one mp_name contains a comma (i.e.
+        individual MPs in 'Lastname, F.' format), ordered by controversy_score
+        descending so the most discriminating motions come first.
+
+        Args:
+            k: maximum number of motion IDs to return.
+
+        Returns:
+            List of motion IDs (ints), sorted by controversy_score DESC.
+        """
+        if duckdb is None:
+            return []
+        try:
+            conn = duckdb.connect(self.db_path, read_only=True)
+            rows = conn.execute(
+                """
+                SELECT DISTINCT mv.motion_id, m.controversy_score
+                FROM mp_votes mv
+                JOIN motions m ON mv.motion_id = m.id
+                WHERE mv.mp_name LIKE '%,%'
+                ORDER BY m.controversy_score DESC, mv.motion_id ASC
+                LIMIT ?
+                """,
+                (int(k),),
+            ).fetchall()
+            conn.close()
+            return [int(r[0]) for r in rows]
+        except Exception:
+            _logger.exception("Error in get_motions_with_individual_votes")
+            return []
+
     def match_mps_for_votes(
         self, user_votes: Dict[int, str], limit: int = 50
     ) -> List[Dict]:

explorer.py

@@ -731,21 +731,20 @@ def build_mp_quiz_tab(db_path: str) -> None:
     if "mp_quiz_asked" not in st.session_state:
         st.session_state["mp_quiz_asked"] = []
 
+    from database import MotionDatabase as _MotionDatabase
+
+    db_inst = _MotionDatabase(db_path)
+
     df = load_motions_df(db_path)
     if df.empty:
         st.warning("Geen moties beschikbaar om de quiz te starten.")
         return
 
-    # seed motions by controversy_score, prefer those with layman_explanation
-    candidates_df = df[df["layman_explanation"].notna()]
-    if candidates_df.empty:
-        candidates_df = df
-    seed = (
-        candidates_df.sort_values(by="controversy_score", ascending=False)
-        .head(SEED_MOTIONS)
-        .copy()
-    )
-    seed_ids = [int(x) for x in seed["id"].tolist()]
+    # seed from motions that actually have individual MP vote records
+    seed_ids = db_inst.get_motions_with_individual_votes(k=SEED_MOTIONS)
+    if not seed_ids:
+        st.warning("Geen individuele stemdata beschikbaar voor de quiz.")
+        return
 
     # Determine next motion to ask
     def _next_motion_id():
@@ -755,13 +754,12 @@ def build_mp_quiz_tab(db_path: str) -> None:
                 return mid
         # otherwise ask discriminating motion based on remaining candidate MPs
         # compute current candidate set
-        from database import db as global_db
 
         try:
             user_votes = {
                 int(k): v for k, v in st.session_state["mp_quiz_votes"].items()
             }
-            ranked = global_db.match_mps_for_votes(user_votes, limit=200)
+            ranked = db_inst.match_mps_for_votes(user_votes, limit=200)
         except Exception:
             ranked = []
 
@@ -770,9 +768,7 @@ def build_mp_quiz_tab(db_path: str) -> None:
         if not candidates:
             return None
         try:
-            next_ids = global_db.choose_discriminating_motions(
-                candidates, excluded, k=1
-            )
+            next_ids = db_inst.choose_discriminating_motions(candidates, excluded, k=1)
             return next_ids[0] if next_ids else None
         except Exception:
             return None
@@ -786,14 +782,20 @@ def build_mp_quiz_tab(db_path: str) -> None:
         if st.button("Reset quiz"):
             st.session_state["mp_quiz_votes"] = {}
             st.session_state["mp_quiz_asked"] = []
-            st.experimental_rerun()
+            st.rerun()
 
     # main question loop (single question per render)
     next_mid = _next_motion_id()
     if next_mid is None:
         st.info("Geen nieuwe vragen beschikbaar om kandidaten te scheiden.")
     else:
-        motion_row = df[df["id"] == next_mid].iloc[0]
+        motion_rows = df[df["id"] == next_mid]
+        if motion_rows.empty:
+            # motion has votes but isn't in the motions DataFrame — skip it
+            st.session_state["mp_quiz_votes"][str(next_mid)] = "Geen stem"
+            st.rerun()
+            return
+        motion_row = motion_rows.iloc[0]
         st.markdown(f"### {motion_row.get('title') or f'Motie #{next_mid}'}")
         if motion_row.get("layman_explanation"):
             st.info(motion_row.get("layman_explanation"))
@@ -808,14 +810,12 @@ def build_mp_quiz_tab(db_path: str) -> None:
         if st.button("Beantwoord en verder", key=f"mp_quiz_submit_{next_mid}"):
             st.session_state["mp_quiz_votes"][str(next_mid)] = choice
             st.session_state["mp_quiz_asked"].append(next_mid)
-            st.experimental_rerun()
+            st.rerun()
 
     # display current ranking
-    from database import db as global_db
-
     try:
         user_votes = {int(k): v for k, v in st.session_state["mp_quiz_votes"].items()}
-        ranking = global_db.match_mps_for_votes(user_votes, limit=50)
+        ranking = db_inst.match_mps_for_votes(user_votes, limit=50)
     except Exception:
         ranking = []
 
@@ -901,9 +901,9 @@ def run_app() -> None:
             build_search_tab(db_path, show_rejected)
         with tab4:
             build_browser_tab(db_path, show_rejected)
-        with tab6:
-            build_mp_quiz_tab(db_path)
         with tab5:
+            build_mp_quiz_tab(db_path)
+        with tab6:
             build_svd_components_tab(db_path)
     else:
         # Fallback for environments where `st.tabs` is not available: use a radio selector