feat: scienting-math/1 sources and derived/math.jsonl; lode references; stress fixes

Math content may say its source is in scienting-math/1's canonical TeX (form,
in no hash); derived/math.jsonl holds papermath's tree, symbols and issues,
and the validator now checks derived files. A symbol annotation names its
symbol by key; lode claim references use lode's tag and pin syntax. The zip
reader refuses entries zipfile cannot read, and checkpoint lines end in LF only.

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

docs/concepts.md

@@ -434,7 +434,7 @@ hale2026harmonic-damb/
   provenance.json        tools, versions and where each stage ran
   assets/                images, by SHA-256
   datasets/              datasets reported from the document
-  derived/               MathML and other renderings, rebuildable
+  derived/               MathML, math trees and other renderings, rebuildable
 ```
 
 Only `MANIFEST.json`, `document.json`, `nodes.jsonl`, `witnesses.json` and `provenance.json` are required, and an optional file with no records is left out; the example package omits `suspects.jsonl`.