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.

config.ts

@@ -72,3 +72,10 @@ export const LEDGER_FILES = {
 	mappings: path.join(PATHS.graph, "mappings.jsonl"),
 	sessions: path.join(PATHS.graph, "sessions.jsonl"),
 } as const;
+
+/**
+ * Notes-import bookkeeping (NOT a ledger): one JSON map, src-id → NotesSource
+ * record (contracts/graph.ts) — the file path + import time + the run's usage
+ * log. Read-modify-write like a chat file, not append-only like the ledgers.
+ */
+export const SOURCES_FILE = path.join(PATHS.graph, "sources.json");