feat: trace annotation body for traced citations; paperspec.traces

A trace follows one citation of a sentence of a citing paper to a passage of the
cited paper (spec/18 section 18.5). Minor change: a new body kind, optional
properties and two rules, with no valid file made invalid.

- annotation schema branch (source, selector, reference, note, verdict, proposer;
  proposer required for a Software creator); body_kind in sql/store.sql; the note
  and proposer terms of the JSON-LD context; rules layer.trace.source and
  layer.trace.target.
- paperspec.traces: resolve(annotation, citing_state, cited_state, same_as) gives
  current, changed, stale, unlinked or misresolved with open and cites; problems,
  disputes, disputed.
- fixtures/records/traces/ on writer2027fixed-ynr7.v3 and vectors/traces.jsonl
  (29 cases); check.py runs the record checks over both layers; counts, glossary,
  examples and CHANGELOG updated.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uy4ZYbWRoCdUtWLEfigysY

fixtures/records/traces/receipt.json

@@ -0,0 +1 @@
+{"at":"2026-10-12T09:30:00Z","by":"ana","doc":"writer2027fixed-ynr7.v3","evidence":[],"format":"scienting-receipt/1","id":"qvckzaatz5d1v","level":"F3","nodes":[],"records":[["annotation","fhnynfb8jx0wc","a1115243473b190f7ed8877780f29c935f29801d6c9fe0b423601247ebf078f8"],["annotation","jh0e4st2c0kpt","b774528344f096051420b6df73c089fdce4d0e1093e4ea3d845fff023c17dee7"]],"rev":0,"root":"d1b96ae5b9887ae843cd209d7da5ea9bb454f1bab77b93d05d38fbfc2b21e826","scope":"targeted:traces","signature":{"key":"ana","scheme":"ed25519","value":"d2xj2bQY3AoDEVV7yzs31mQpMoGre+V919NUM/Ba/qj+ySb1QKs7D9ZidM6+ksl1xlNsCLNU2rdeclUduoZZBA=="}}