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

fixtures/packages/hale2026harmonic-damb/derived/math.jsonl

@@ -0,0 +1,3 @@
+{"complete":true,"form":"scienting-math/1","issues":[],"node":"tkxsmts","run":null,"symbols":["E_{\\text{bond}}","K_{r}","r","r_{\\text{eq}}"],"tool":{"name":"papermath","version":"0.1.0"},"tree":["rel",["sym","E_{\\text{bond}}"],"=",["mul",["frac",["num","1"],["num","2"]],["sym","K_{r}"],["pow",["add",["sym","r"],["neg",["sym","r_{\\text{eq}}"]]],["num","2"]]]]}
+{"complete":true,"form":"scienting-math/1","issues":[],"node":"rr20tev","run":3,"symbols":["K_{r}"],"tool":{"name":"papermath","version":"0.1.0"},"tree":["sym","K_{r}"]}
+{"complete":false,"form":"scienting-math/1","issues":[{"at":"_{2}","code":"opaque","message":"a part after the formula's end"}],"node":"hca6dc5","run":1,"symbols":[],"tool":{"name":"papermath","version":"0.1.0"},"tree":["opaque","_{2}"]}