feat: comment categories; emend, relink and resolve corrections

scienting-layer/1: an optional, fixed category on comment, caveat and
question bodies (comment, context, critique, question, correction,
feedback, resource).

Corrections: emend fixes the authors' own slip and keeps what was printed
(a run's printed), never lowering fidelity or a witness match; relink sets
or removes what a citation names; resolve sets a reference's resolution.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017R7sgDNvUGWY2zFPCq2JH6

fixtures/records/layer/layer.json

@@ -1 +1 @@
-{"@context":["http://www.w3.org/ns/anno.jsonld","https://paperspec.scient.ing/context/scienting-1.jsonld"],"audience":"student","created":"2026-10-11T19:00:00Z","creator":{"id":"tag:scient.ing,2026:key:ana","name":"Ana Example","type":"Person"},"docs":["smithlab/hale2026harmonic-damb"],"format":"scienting-layer/1","id":"tag:scient.ing,2026:layer:smithlab/kp4m2x7q","label":"Smith lab reading of Hale and Osei","license":{"spdx":"CC-BY-4.0"},"project":"smithlab-charges","purpose":"Glosses, claim links and exercises for new students.","total":10,"type":"AnnotationCollection","visibility":"team"}
+{"@context":["http://www.w3.org/ns/anno.jsonld","https://paperspec.scient.ing/context/scienting-1.jsonld"],"audience":"student","created":"2026-10-11T19:00:00Z","creator":{"id":"tag:scient.ing,2026:key:ana","name":"Ana Example","type":"Person"},"docs":["smithlab/hale2026harmonic-damb"],"format":"scienting-layer/1","id":"tag:scient.ing,2026:layer:smithlab/kp4m2x7q","label":"Smith lab reading of Hale and Osei","license":{"spdx":"CC-BY-4.0"},"project":"smithlab-charges","purpose":"Glosses, claim links and exercises for new students.","total":11,"type":"AnnotationCollection","visibility":"team"}