Centralized model config (config.ts MODELS) + extraction seam logging

MODELS in config.ts is now THE single tuning table: model id + OpenRouter
reasoning effort for teacher/researcher/demoBuilder/visualMaker/extractor/
auditor. .env.local is secrets-only (LH_* model vars removed; all sub-agents
previously had NO reasoning setting -> provider-default unbounded thinking,
the extraction token burn). One factory (src/agent/models.ts modelFor) wires
all six call sites; test injection unchanged. EXTRACTION.everyNQuizAnswers
moved to a config literal too. Plus the §5 one-line-per-seam logging in the
extraction pipeline: pipeline start, extractor/auditor start + per-step,
audit kept, merged — previously silent until completion, which made live
runs look like they never fired.

src/agent/models.ts

@@ -0,0 +1,17 @@
+import { openrouter } from "@openrouter/ai-sdk-provider";
+import type { LanguageModel } from "ai";
+import { MODELS, type ModelRole } from "../../config.ts";
+
+/**
+ * The one factory every agent's model comes from. Model choice and thinking
+ * budget live in config.ts (MODELS) — the single tuning table; this module
+ * only wires them to OpenRouter. `effort: "none"` is OpenRouter's off-switch
+ * for reasoning tokens; higher levels let the model think longer (and bill
+ * accordingly).
+ */
+export function modelFor(role: ModelRole): LanguageModel {
+	const spec = MODELS[role];
+	return openrouter(spec.model, {
+		reasoning: { enabled: true, effort: spec.effort },
+	});
+}