feat(skill): add score-extremity project-local skill

Two-dimensional scoring via subagents:
- Stijl-extremiteit: stylistic/inflammatory language (1-5)
- Materiele impact: substantive rights/policy impact (1-5)
Defines prompt template, output JSON schema, and batch subagent workflow.

.opencode/skills/score-extremity/SKILL.md

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+---
+name: score-extremity
+description: Two-dimensional extremity scoring for Dutch parliamentary motions. Use when scoring policy radicalism along stylistic vs material impact dimensions, or when performing LLM-based analysis of motion text extremity.
+---
+
+# Two-Dimensional Extremity Scoring
+
+Score Dutch parliamentary motions on TWO independent dimensions:
+
+1. **Stijl-extremiteit (stylistic extremity, 1–5):** How inflammatory, harsh, or rhetorically charged is the language? 1 = neutral/technical, 5 = openly hostile/discriminatory language.
+
+2. **Materiele impact (material impact, 1–5):** How much would this policy actually restrict rights, affect specific groups, or reshape institutions if enacted? 1 = procedural/ministerial request, 5 = fundamental rights restriction or institutional dismantling.
+
+These dimensions are independent. A motion can be:
+- High stylistic, low material: "Alle buitenlanders moeten het land uit!" (inflammatory but legally vacuous)
+- Low stylistic, high material: "Het recht op gezinshereniging wordt beperkt tot kerngezin met inkomenseis van 150% minimumloon" (measured language but concretely restricts rights)
+
+## Scoring Prompt
+
+```text
+Beoordeel de volgende motie op TWEE onafhankelijke dimensies:
+
+MOTIE:
+Titel: {title}
+Tekst: {text}
+Vereenvoudigde uitleg: {layman}
+
+1) STIJL-EXTREMITEIT (1-5):
+Hoe fel/opruiend/geladen is het taalgebruik? Let op woordkeuze, toon, en retorische middelen.
+1 = neutraal/technisch/ambtelijk, 3 = stellige politieke taal/waardeoordelen, 5 = vijandig/discriminerend/haatdragend taalgebruik.
+
+2) MATERIELE IMPACT (1-5):
+Hoe ingrijpend is het voorgestelde beleid als het wordt uitgevoerd? Wie wordt geraakt en hoe?
+1 = procedureel/symbolisch/verzoek aan minister, 3 = concrete beleidswijziging met meetbare gevolgen, 5 = fundamentele inperking van rechten/ontmanteling van instituties/grootschalige uitsluiting.
+
+Geef voor elke dimensie een score van 1-5 en een korte toelichting in het Nederlands.
+```
+
+## Output Schema
+
+Return a JSON object with this structure:
+
+```json
+{
+  "stijl_extremiteit": 3,
+  "stijl_toelichting": "Gebruikt termen als 'massa-immigratie' en 'tsunami' maar niet direct discriminerend",
+  "materiele_impact": 4,
+  "materiele_toelichting": "Beperkt recht op gezinshereniging tot kerngezin met verzwaarde inkomenseis"
+}
+```
+
+Field constraints:
+- `stijl_extremiteit`: integer, 1–5
+- `stijl_toelichting`: string, Dutch, 1–3 sentences
+- `materiele_impact`: integer, 1–5
+- `materiele_toelichting`: string, Dutch, 1–3 sentences
+
+## Batch Scoring
+
+When scoring multiple motions at once, return a JSON array:
+
+```json
+{
+  "motions": [
+    {
+      "motion_id": 123,
+      "stijl_extremiteit": 3,
+      "stijl_toelichting": "...",
+      "materiele_impact": 4,
+      "materiele_toelichting": "..."
+    }
+  ]
+}
+```
+
+## Subagent Workflow
+
+The orchestrator spawns subagents (deepseek v4 flash) to score motions in batches:
+
+1. Read this skill file to get the prompt template and schema
+2. Query the stratified sample from `right_wing_motions` JOIN `extremity_scores`
+3. Format batches of 10 motions each
+4. For each batch, spawn a subagent (`task` tool, subagent_type: general) with:
+   - This skill's prompt template filled with the 10 motions' text and layman explanations
+   - The output schema as the expected return format
+   - Instruction to return valid JSON matching the `motions` array schema
+5. Collect results, validate against schema, store in `extremity_scores_2d` table
+6. Compute Pearson r between `stijl_extremiteit` and `materiele_impact`
+
+Batch dispatch is parallel: all 10 subagents (for 100 motions) can be spawned simultaneously since they have no inter-dependencies.