feat(licence): contributed manifests are CC0 1.0

Contributed manifests were in no declared condition at all, which left §9a
replication with no grant flowing through it: peers mirror each other's
catalogues wholesale, and every hop of that was unlicensed.

CC0 rather than a share-alike licence, because a share-alike works by asserting
a right in the data and then conditioning its use. The position in
docs/legal-posture.md §3 is that presence timings are facts rather than
protectable expression — asserting copyright in them in order to license them
would contradict that argument in the same repository, and that contradiction is
worth more to an opponent than the licence is worth to us. CC0 also waives the
sui generis database right by name, closing the EU-specific residual exposure
from the contributor's side.

The grant is taken at token issuance, and that is not incidental. There are no
accounts, so there is no sign-up to attach terms to, and a manifest arrives over
POST /manifests with no channel to negotiate over. Acquiring the contribute
capability is the only moment a grant can be made, so POST /tokens now returns
the licence and its terms alongside the token — a licence the server publishes
but never delivers is one no contributor agreed to.

The test pins the scope limit as well as the identifier. Bounding the grant to
the manifest is the half that can fail silently: a reworded term reading onto
the underlying work would purport to grant what no contributor can.

Also records the settled code-licence position across all four repositories in
the legal posture, correcting an earlier claim there that the plugin and
extraction repos declared nothing. Both already carried LICENSE files.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TRACES: UR-019 | PR-006

tests/api.rs

@@ -218,6 +218,25 @@ async fn tokens_are_issued_anonymously_and_are_distinct() {
     assert!(a.starts_with("jray_"));
 }
 
+#[tokio::test]
+async fn the_token_response_carries_the_contribution_licence() {
+    // §5b / UR-019. There are no accounts, so token issuance is the only moment
+    // a grant can be taken — a licence the server publishes but never delivers
+    // is one no contributor agreed to, which is precisely the gap that leaves
+    // federated replication (UR-008) without a grant flowing through it.
+    let s = TestServer::new("token-licence");
+    let (status, body, _) = s.post_json("/api/v1/tokens", &json!({})).await;
+    assert_eq!(status, StatusCode::OK, "body: {body}");
+
+    assert_eq!(body["contribution_license"].as_str(), Some("CC0-1.0"));
+
+    let terms = body["contribution_terms"].as_str().expect("terms in response");
+    assert!(terms.contains("CC0 1.0"), "terms must name the licence: {terms}");
+    // The scope limit is the operative half: it must be impossible to read the
+    // grant as covering the film rather than the manifest.
+    assert!(terms.contains("manifest only"), "terms must bound the grant to the manifest: {terms}");
+}
+
 // ---------------------------------------------------------------------------
 // §6 — upload validation
 // ---------------------------------------------------------------------------