feat(overton): coalition coding fix + regenerate breakpoint analysis

reports/overton_window/breakpoint_analysis.md

@@ -45,8 +45,8 @@ These are descriptive, not inferential — with only 8 pre-2024 years and 3 post
 
 | Metric | Pre-2024 Mean | Post-2024 Mean | Δ | Cohen's d | N pre / N post |
 |--------|--------------|---------------|-----|-----------|---------------|
-| Centrist Support | 0.130 | 0.437 | +0.307 | +0.88 | 1295 / 405 |
-| Extremity | 2.28 | 2.18 | -0.10 | -0.14 | 1295 / 405 |
+| Centrist Support | 0.130 | 0.423 | +0.293 | +0.85 | 1295 / 437 |
+| Extremity | 2.28 | 2.17 | -0.10 | -0.14 | 1295 / 437 |
 
 **Interpretation gate:** If opposition metrics also rise post-2024, the shift is not
 purely coalition-driven. If opposition metrics stay flat while overall metrics rise,
@@ -54,7 +54,7 @@ the shift is coalition-specific.
 
 ## 3. Coalition Composition
 
-2016-2017: Rutte II (VVD/PvdA). 2018-2021: Rutte III (VVD/CDA/D66/CU). 2022-2023: Rutte IV (VVD/D66/CDA/CU). 2024-2026: Schoof (PVV/VVD/NSC/BBB). 2024 ambiguous: Schoof cabinet started July 2024; all 2024 motions are coded to the Schoof coalition. Coalition effect may be overestimated for early 2024.
+2016-2017: Rutte II (VVD/PvdA). 2018-2021: Rutte III (VVD/CDA/D66/CU). 2022-2023: Rutte IV (VVD/D66/CDA/CU). 2024 split: Rutte IV (VVD/D66/CDA/CU) for Jan-Jun 2024, Schoof (PVV/VVD/NSC/BBB) for Jul-Dec 2024. 2025-2026: Schoof (PVV/VVD/NSC/BBB). Period detection uses motion date, not just year.
 
 Submitter party is parsed from motion title prefixes
 (e.g., "Motie van het lid Wilders over ..."). Only the lead submitter's party is