feat: rename to paperspec and add the website

- Rename manuspec to paperspec everywhere outside pixi.toml: prose, the
  tools, provenance tool names and the fixture key derivations, so every
  fixture and vector is rebuilt.
- Move the namespace addresses under the site, mirroring the repository:
  schema $id https://paperspec.scient.ing/schemas/<file>, the JSON-LD
  context https://paperspec.scient.ing/context/scienting-1.jsonld, and
  term IRIs https://paperspec.scient.ing/vocab#<term>. Format
  identifiers (scienting-*) and URNs (urn:scienting:) are unchanged.
- tools/site.py (standard library only) builds _site/: every file of the
  repository at its own path, each Markdown file rendered as a page with
  sidebar navigation, heading anchors matching the forge's, folder
  listings, a vocabulary page for the context's IRIs, a heading search
  and a 404 page; light and dark themes.
- check.py builds the site and checks that every Markdown file has a
  page, every internal link and fragment resolves, no Markdown is left
  unrendered, and every $id, the context address and the vocabulary IRIs
  are files of the site.
- deploy/: a Caddyfile with the media types and CORS the data needs, and
  a guide; .gitea/workflows/site.yml builds on main and publishes with
  rsync when the SITE_* secrets are set.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

fixtures/invalid/manifest-key/package/MANIFEST.json

@@ -1 +1 @@
-{"doc":"scienting-doc/1","files":[{"path":"document.json","sha256":"20a7d6ba83bf42a87e44f3b3f96bfb16ff545b199d82e54d3c17989e465281df","size":555},{"path":"nodes.jsonl","sha256":"ffeffbf15cc9fe8182a31ef0bac32c1aef8c7a119706ac1e8a55aad218d0622c","size":11295},{"path":"provenance.json","sha256":"b1af404b3a07d4b102f0a45237285315dc1ff60f243636c22aef3e1c20b46912","size":224},{"path":"receipts.jsonl","sha256":"e6be2c6ff4d1444e2faf75c8c4d03482ceaf49746ea390592928b2b5e3b22237","size":2180},{"path":"references.jsonl","sha256":"bb5445037c28bf5fde215b4b831c29327dec6dd88259e2d53aabb995f2fdb98f","size":60},{"path":"roster.json","sha256":"7ee0c38fb4fdfc15d4ffa8139a239c23082dc69f8147c5920a39e8361cc7bbeb","size":924},{"path":"witnesses.json","sha256":"83ac4411c2efe65e0f7fc4c9336abbef6977cd32b0f90de029a7f8516afc3e97","size":750}],"format":"scienting-package/1","key":"other2026example"}
+{"doc":"scienting-doc/1","files":[{"path":"document.json","sha256":"20a7d6ba83bf42a87e44f3b3f96bfb16ff545b199d82e54d3c17989e465281df","size":555},{"path":"nodes.jsonl","sha256":"ffeffbf15cc9fe8182a31ef0bac32c1aef8c7a119706ac1e8a55aad218d0622c","size":11295},{"path":"provenance.json","sha256":"4bc7649bf6d3113f6c72b4016713654f57c8f03069632eabd1e6025c05cb9dac","size":226},{"path":"receipts.jsonl","sha256":"3f610039a8f883356201b63c9ad31afee630ebcbc0cc33bfb989a55716db85f0","size":2180},{"path":"references.jsonl","sha256":"bb5445037c28bf5fde215b4b831c29327dec6dd88259e2d53aabb995f2fdb98f","size":60},{"path":"roster.json","sha256":"4a6d29e8968143a4e19f485741c513245df1de77eec4ef9b3047c71db45cda22","size":924},{"path":"witnesses.json","sha256":"83ac4411c2efe65e0f7fc4c9336abbef6977cd32b0f90de029a7f8516afc3e97","size":750}],"format":"scienting-package/1","key":"other2026example"}