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

context/scienting-1.jsonld

@@ -25,6 +25,7 @@
     "reason": "sct:reason",
     "reference": "sct:reference",
     "for": "sct:questionFor",
+    "category": "sct:category",
     "generator": "sct:generatedBy",
     "exercise": {
       "@id": "sct:exercise",