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/records/checklist/receipt.json

@@ -1 +1 @@
-{"at":"2026-10-12T11:30:00Z","by":"ana","doc":"hale2026harmonic","evidence":[{"kind":"source-file","note":"The exported HTML.","sha256":"abfea8185834a5da9aeeb19a530e3444092c5d7887306dad93168609f848d1c0"}],"format":"scienting-receipt/1","id":"jv2mdcw0kvs29","level":"F3","nodes":[],"records":[["checklist","svbx4658yvm4c","0fdafa43151edd08cb470e3db528e134850d342c5e071e6d17bc9a41f5898345"]],"rev":12,"root":"e882efbe76a7e35938f0f8e087b9a1cf544f5151b7abafc67e85dbf155329cd4","scope":"targeted:checklist","signature":{"key":"ana","scheme":"ed25519","value":"bZ8LY9BzrImifD4Q5F6fUYooMs8229gDNhtVy/JNilnrRr6Wmx86TbuBMQ53aIe1q85NR75LQxkEdT190AVrBw=="}}
+{"at":"2026-10-12T11:30:00Z","by":"ana","doc":"hale2026harmonic","evidence":[{"kind":"source-file","note":"The exported HTML.","sha256":"abfea8185834a5da9aeeb19a530e3444092c5d7887306dad93168609f848d1c0"}],"format":"scienting-receipt/1","id":"jv2mdcw0kvs29","level":"F3","nodes":[],"records":[["checklist","svbx4658yvm4c","0fdafa43151edd08cb470e3db528e134850d342c5e071e6d17bc9a41f5898345"]],"rev":12,"root":"e882efbe76a7e35938f0f8e087b9a1cf544f5151b7abafc67e85dbf155329cd4","scope":"targeted:checklist","signature":{"key":"ana","scheme":"ed25519","value":"Xnt7xmt2Xy1xtCn55/IvAfWvIM+NygQY1YDqGAP+APPrzjIym9ddsFWqECw7N9mJIYR2bmJuXlVqdpydnr8CAA=="}}