Extraction-UX data layer: the chunk budget becomes a graph setting; the chat view gets a per-session coverage read

Owner-locked extraction-UX redesign (dispatch 2026-09-24), part 1 (data
layer; the UI chunk follows).

THRESHOLD -> SETTING
- config.ts's EXTRACTION.chunkTokens dies; the default moves into
  FACTORY_SETTINGS.graph.extractionChunkTokens (4096, the old constant's
  value). GraphSettings gains the optional field, Required at resolution
  via the standard ?? FACTORY pattern — pre-redesign records resolve the
  default cleanly.
- FLOOR 500 (the implementer's call, documented on the field): every run
  pays the graph-carrying prompt overhead out of the write channel's
  money — a smaller budget fires penny-batches that cost more per
  extracted token than the content is worth. The sanitizer CLAMPS up
  (bd68486 clamp-never-reject discipline: fractions floor, junk drops);
  the settings PUT REJECTS below-floor with the rationale in the message.
  No ceiling: a large budget just delays extraction — the user's stated
  cost/thoroughness tradeoff, not a misconfiguration to police.
- The trigger (turn-service.triggerExtraction) takes the budget as a
  parameter — chat-handler passes effective.graph.extractionChunkTokens,
  the fresh per-turn read, same as every other gate.
- The pipeline's BATCH side threads through the same number:
  ExtractionPipelineDeps gains an OPTIONAL getChunkTokens getter with the
  factory default (Teacher's 24 test fixtures stay untouched; the two
  call-site lines inside extraction.ts are the only cross-band edits,
  flagged). chat-handler + backfill/import-notes wire the live
  effectiveSettings — trigger and batches share one budget, always.

PER-SESSION COVERAGE READ
- sessionCoverage(chatId) (server/chats.ts): the chat view's ring-meter
  block — totalMessages/coveredCount/uncoveredCount/coveredTokens/
  uncoveredTokens (the same coverageOf derivation /api/graph/coverage
  serves, scoped to one chat), running (chat-kind extraction registered
  for this id), and lastFoldedAt (the chat's newest coverage row's fold
  — a cheap single pass; null before any fold). GET /api/chats/[id]
  carries it as coverage: {...}; unknown chat -> null (the route 404s
  first).
- /api/graph/coverage (the all-sessions list) compiles untouched — the
  per-session read is a scoping of it, not a supersession; the UI's
  sidebar/ring chunk decides which surface it consumes.

Tests: factory/sanitizer pins (clamp-up, fraction-floor, junk-drop),
resolution pins (absent -> 4096, stored 2000 wins), settings-body pins
(valid/absent/fraction/below-floor 400/junk 400), sessionCoverage pins
(derived split, newest-fold scoping, cross-session isolation, running via
the registry, null on unknown chat). 893/893.

src/agent/subagents/extraction.ts

@@ -4,7 +4,7 @@ import type { Usage } from "@earendil-works/pi-ai";
 import { z } from "zod";
 import { lhTool, toPiTools } from "../lh-tool.ts";
 import type { ModelRole } from "../../../config.ts";
-import { ModelsNotConfiguredError, ROLE_SLOT, type ModelSlotName } from "../../core/settings.ts";
+import { FACTORY_SETTINGS, ModelsNotConfiguredError, ROLE_SLOT, type ModelSlotName } from "../../core/settings.ts";
 import type { PiEngine } from "../models.ts";
 import { runSubagent } from "./pi-run.ts";
 import type {
@@ -20,7 +20,6 @@ import { getGraph, mergeFindings, type EmissionStats, type GraphDeps } from "../
 import type { GraphStore } from "../../core/ports.ts";
 import { settleGraphLayout } from "../../core/layout-settle.ts";
 import { batchRuns, batchTag, coverageOf, messageViewLines } from "../../core/coverage.ts";
-import { EXTRACTION } from "../../../config.ts";
 
 /**
  * The extraction pipeline (vision §1 construction, 2026-09-02 redesign) — the
@@ -569,7 +568,15 @@ export interface ExtractionModels {
 	engineFor?: (role: ModelRole) => PiEngine | undefined;
 }
 
-export interface ExtractionPipelineDeps extends GraphDeps, ExtractionModels {}
+export interface ExtractionPipelineDeps extends GraphDeps, ExtractionModels {
+	/** The chunk budget — the transcript-token share of the extractor's
+	 *  context; batches fill to it (the trigger fires on the same number,
+	 *  read fresh per turn by the composition root). OPTIONAL with the
+	 *  factory default (4096) so test fixtures stay minimal; the server
+	 *  callers wire the live effective settings (extraction-UX redesign,
+	 *  2026-09-24). */
+	getChunkTokens?: () => number;
+}
 
 export interface NotesImportInput {
 	/** The source's file path — its identity (deterministic src id) AND its
@@ -760,10 +767,11 @@ export function createExtractionPipeline(deps: ExtractionPipelineDeps): Extracti
 				console.info(`[extraction ${chatId}] nothing uncovered — no-op`);
 				return { nodes: 0, edges: 0, events: 0 };
 			}
-			const batches = batchRuns(covered.uncovered, EXTRACTION.chunkTokens);
+			const chunkTokens = deps.getChunkTokens?.() ?? FACTORY_SETTINGS.graph.extractionChunkTokens;
+			const batches = batchRuns(covered.uncovered, chunkTokens);
 			console.info(
 				`[extraction ${chatId}] pipeline start — ${covered.uncoveredTokens} uncovered tok, ` +
-					`${covered.uncoveredCount} messages, ${batches.length} batch(es) of ≤${EXTRACTION.chunkTokens} tok`,
+					`${covered.uncoveredCount} messages, ${batches.length} batch(es) of ≤${chunkTokens} tok`,
 			);
 			for (const batch of batches) {
 				// The batch's prompt view: SESSION header + the batch's lines,