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

spec/20-projects.md

@@ -7,7 +7,7 @@ A project, `scienting-project/1`, is the unit a team works in.
 | `key`, `store`, `name`, `description` | Its identity. |
 | `members` | People with a `role` (`owner`, `editor`, `reader` or `guest`) and the roster keys they sign with. |
 | `documents` | The project's documents, each with the `reason` it is included, `tags`, and a reading `status` per member: `unread`, `reading` or `read`. |
-| `paths` | Reading paths: ordered steps through documents, nodes, claims and layers, for onboarding a student or preparing a reading group. |
+| `paths` | Reading paths: ordered steps through documents, nodes, claims and layers, for onboarding a student or preparing a reading group; a claim step's `ref` is a claim reference, `lode:<tag>` ([18.4](18-layers.md#184-bodies)). |
 | `layers`, `datasets`, `views`, `drafts` | What the project holds. |
 | `claims` | The claim namespace or bundle it uses, as the `lode` setting. |
 | `settings` | The digit rule for targeted F3 ([8.10](08-fidelity.md#810-targeted-f3)), the drift threshold ([6.6](06-anchors.md#66-drift)), the spot-check rate and minimum ([8.8](08-fidelity.md#88-spot-checks)), what happens when a right is unknown (`refuse`, the default, or `warn`), the stage requirements in use, as the `id` of their stage file ([14](14-rights.md)), and the project's transparency `log`: its `origin`, the roster keys that `witness` it, and the `threshold` of witnesses a checkpoint needs ([23](23-log.md)). |