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

schemas/common.schema.json

@@ -71,6 +71,22 @@
       "type": "string",
       "pattern": "^([a-z0-9][a-z0-9._-]*/)?[a-z][a-z0-9]*-[0-9a-hjkmnp-tv-z]{4,51}(\\.[a-z0-9][a-z0-9-]*)*#[a-z0-9][a-z0-9._-]*(@[0-9a-f]{6})?(\\[(0|[1-9][0-9]*):(0|[1-9][0-9]*)\\])?$"
     },
+    "claimRef": {
+      "type": "string",
+      "pattern": "^lode:([a-z0-9.-]+\\.[a-z]{2,}/)?[0-9A-HJKMNP-TV-Z]{8}$",
+      "description": "A claim in a lode store: lode:TAG, or lode:host/TAG for another store, TAG eight Crockford base32 capitals (spec/18 §18.4)."
+    },
+    "claimPin": {
+      "type": "string",
+      "pattern": "^lode:([a-z0-9.-]+\\.[a-z]{2,}/)?[0-9A-HJKMNP-TV-Z]{8}@[0-9a-f]{6}$",
+      "description": "A claim pinned to its statement: the claim's reference, @ and the first six hex digits of its statement hash (spec/18 §18.4)."
+    },
+    "mathForm": {
+      "enum": [
+        "scienting-math/1"
+      ],
+      "description": "The form a math source is spelled in; scienting-math/1 is canonical TeX (spec/03 §3.7, spec/09 §9.4)."
+    },
     "time": {
       "type": "string",
       "pattern": "^[0-9]{4}-[0-1][0-9]-[0-3][0-9]T[0-2][0-9]:[0-5][0-9]:[0-6][0-9]Z$"