delete the batch practice-problems module (superseded by practice sessions)

Owner ruling 2026-10-04: the module is a sunk cost, retrievable from
history if ever revisited. Removed: core practice contracts + pipeline
helpers, the PracticeStore port + adapter + data dir path, server
service + API routes (sets, clusters picker, practice aborts), the
practice pages + dialog/exam/list UI, chain-table's Generate handoff,
sidebar nav, activity-dock practice rows, and the partitioner/
problemGenerator/grader model roles (BACKGROUND_MODEL_ROLES 8 → 5).

Survivors, moved to core/chains.ts (pure + browser-safe): ReasoningChain,
chainsForSelection, formatChainLine — the chain table and graph
emission still consume them.

config.ts

@@ -26,10 +26,6 @@ export const PATHS = {
 	/** Chat sessions (AI SDK UIMessage transcripts, one JSON file per chat). */
 	chats: path.join(DATA_ROOT, "chats"),
 	graph: path.join(DATA_ROOT, "graph"),
-	/** Practice problem sets (one JSON document per set — src/store/practice.ts).
-	 * Bounded self-contained snapshots (propositions + chains frozen at
-	 * creation), not append-only ledgers. */
-	practice: path.join(DATA_ROOT, "practice"),
 	/** Debug artifacts (env-gated): data/debug/provider-events/<chatId>.jsonl
 	 * raw provider stream recordings (src/agent/provider-events.ts). */
 	debug: path.join(DATA_ROOT, "debug"),
@@ -56,10 +52,7 @@ export type ModelRole =
 	| "visualMaker"
 	| "pdfReader"
 	| "extractor"
-	| "auditor"
-	| "partitioner"
-	| "problemGenerator"
-	| "grader";
+	| "auditor";
 
 /**
  * The LIVE graph store (src/store/graph.ts) — owned by the app's extraction