Notes front door: format-agnostic import into the graph pipeline

The same extractor→auditor→merger pipeline now runs over raw personal
notes in arbitrary formats (vision §1, DECIDED 2026-09-13):

- NotesSource records (data/graph/sources.json, deterministic id from
  path hash → idempotent re-imports) play the chatId role in mappings,
  checkpoints, and observation events; usage lands on the source record
  (appendSourceUsage, idempotent per startedAt, kept across upserts).
- mergeFindings is chat-store-free: callers pass MergeSource
  {messages, foldedAt} — sessions pass the chat record, notes pass
  messages:null (no quiz-event rebuild; a deterministic rebuild needs
  structured quiz tool parts).
- Second extractor prompt (NOTES_EXTRACTOR_INSTRUCTIONS) for general-
  purpose extraction; understanding judges the AUTHOR's grasp. Auditor
  wording input-agnostic. extract/audit share one generic runSubmitAgent.
- graphSnapshot.fileSources (srcId→filePath); notes sources render as
  static path entries in the detail card (FileTextIcon, never a link).
- One shared pipeline instance (exported from chat-handler): same
  single-flight registry, live status chips (label = file path), usage
  accounting, and true abort for both front doors.
- Transport: POST /api/graph/import (multipart, 3-wide worker pool) +
  Import notes… button in the graph view; scripts/import-notes.ts for
  batch runs (concurrency 4).
- real-data-extraction/ gitignored (raw import sources never committed).

355/355 tests; typecheck, lint, build green.

src/core/ports.ts

@@ -24,6 +24,7 @@ import type {
 	PlanTree,
 	SessionCheckpoint,
 	TurnUsage,
+	NotesSource,
 } from "./contracts.ts";
 
 // ─── ChatStore — the session record's home (data/chats) ─────────────────────
@@ -80,6 +81,15 @@ export interface GraphStore {
 	/** Append one emission checkpoint. */
 	appendCheckpoint(checkpoint: SessionCheckpoint): void;
 	readCheckpoints(): SessionCheckpoint[];
+
+	/** Upsert one imported-notes source record (config.SOURCES_FILE — a
+	 *  JSON map, not a ledger; an upsert keeps the existing usage log). */
+	upsertSource(source: NotesSource): void;
+	/** Every notes source record, by id order-insensitive. */
+	readSources(): NotesSource[];
+	/** Append one run's usage to a source record — idempotent per
+	 *  startedAt, mirroring ChatRecord.extractions. */
+	appendSourceUsage(id: string, entry: ExtractionRunUsage): void;
 }
 
 // ─── JobStore — background sub-agent jobs (data/jobs) ─────────────────────────