refactor!: claim references are claim:TAG

lode is renamed paperclaim. A claim reference is claim:TAG or
claim:host/TAG and a pin claim:TAG@hex6 (claimRef and claimPin in
common.schema.json, spec/18 §18.4, spec/02, spec/20); the eight-character
tags do not change. A project names its claim namespace as
claims.paperclaim, and the main example's targeted receipts take the
scope targeted:paperclaim. No old prefix or name is accepted.

paperspec build regenerated the fixtures and vectors: the claim link's and
the symbol's record IDs, the layer receipt, project.json, the two targeted
receipts and Ben's spot-check, the QA report, the inclusion proof, the log's
checkpoint and tiles, and the signature, spot-check, VRF and checkpoint
vectors. The walkthrough and examples quote the new receipt IDs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SarHTuHhV9cS85XWy2NrLJ

fixtures/records/checkpoint.json

@@ -1 +1 @@
-{"format":"scienting-checkpoint/1","note":"scient.ing/log/smithlab\n9\nGa0n103p3Gl136z6XWmM92kGvsvMYGXlk+ijjX4KWiA=\n\n— ana dBv7wtCAdNnczkCO5KwtrmDvtWUVPRusBSuLPeBDQoLZi9Hm34IHuNjvnjyPEar5afNf7xqcDtokk2XZEP31uJMVuwE=\n— wit h7ghDsJGkhWLaPO7+TIZQUenslhiQh/E/TKWU4ddphpFcuylQBZM2kG/o8H1nyPfUT0MkbvnFqPFfHPH3OaN5W1EwAI=\n","origin":"scient.ing/log/smithlab","root":"19ad27d74de9dc6975dfacfa5d698cf76906becbcc6065e593e8a38d7e0a5a20","signatures":[{"key_hash":"741bfbc2","name":"ana","value":"0IB02dzOQI7krC2uYO+1ZRU9G6wFK4s94ENCgtmL0ebfgge42O+ePI8Rqvlp81/vGpwO2iSTZdkQ/fW4kxW7AQ=="},{"key_hash":"87b8210e","name":"wit","value":"wkaSFYto87v5MhlBR6eyWGJCH8T9MpZTh12mGkVy7KVAFkzaQb+jwfWfI99RPQyRu+cWo8V8c8fc5o3lbUTAAg=="}],"size":9}
+{"format":"scienting-checkpoint/1","note":"scient.ing/log/smithlab\n9\nWQxnIeoDxqOJ/rIz5b0uJ3pfpq4S1kUQMNvbG55bPEM=\n\n— ana dBv7wrLxQN8XFJOwKZO4L98UosXwyw3jVbYTM3a+dZWQdtZkPqd6fM8LHwgbIyBT+OEq18meE0JkqJKoYeZ2DMP7eAo=\n— wit h7ghDsbQuWAI5VIGw+jiEAMHeSpDVlubOR46YIEuxL5TWkxU1xAtrp4gwgKxCV+q72A9mZC6APgyaCAUi78euiV/SA8=\n","origin":"scient.ing/log/smithlab","root":"590c6721ea03c6a389feb233e5bd2e277a5fa6ae12d6451030dbdb1b9e5b3c43","signatures":[{"key_hash":"741bfbc2","name":"ana","value":"svFA3xcUk7Apk7gv3xSixfDLDeNVthMzdr51lZB21mQ+p3p8zwsfCBsjIFP44SrXyZ4TQmSokqhh5nYMw/t4Cg=="},{"key_hash":"87b8210e","name":"wit","value":"xtC5YAjlUgbD6OIQAwd5KkNWW5s5HjpggS7EvlNaTFTXEC2uniDCArEJX6rvYD2ZkLoA+DJoIBSLvx66JX9IDw=="}],"size":9}