feat: per-archive license normalization

Per sub-project-2 plan Task 6 / spec §5.3. normalize_license maps CC URLs /
identifiers and public-domain markers to the LICENSES vocab, builds non-empty
attribution for cc_by/cc_by_nc, and rejects unmappable licenses at ingest.
librivox_license() helper returns public_domain.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_licensing.py

@@ -0,0 +1,84 @@
+import pytest
+
+from hef.catalog import LICENSES
+from tools.licensing import librivox_license, normalize_license
+
+
+def test_cc_by_url_maps_and_requires_attribution():
+    lic, attr = normalize_license(
+        "https://creativecommons.org/licenses/by/4.0/", creator="Jane Doe"
+    )
+    assert lic == "cc_by" and "Jane Doe" in attr
+
+
+def test_cc_by_identifier_maps():
+    lic, attr = normalize_license("CC BY 4.0", creator="Sam")
+    assert lic == "cc_by" and attr
+
+
+def test_cc_by_nc_maps():
+    lic, attr = normalize_license(
+        "https://creativecommons.org/licenses/by-nc/4.0/", creator="Artist"
+    )
+    assert lic == "cc_by_nc" and "Artist" in attr
+
+
+def test_cc_by_without_creator_still_has_nonempty_attribution():
+    # validate() rejects an attribution license with empty attribution, so the
+    # normalizer must always produce a non-empty string for cc_by/cc_by_nc.
+    lic, attr = normalize_license("https://creativecommons.org/licenses/by/4.0/")
+    assert lic == "cc_by" and attr != ""
+
+
+def test_cc0_maps_with_empty_attribution():
+    lic, attr = normalize_license("https://creativecommons.org/publicdomain/zero/1.0/")
+    assert lic == "cc0" and attr == ""
+
+
+def test_cc0_identifier():
+    lic, attr = normalize_license("CC0")
+    assert lic == "cc0" and attr == ""
+
+
+def test_public_domain_mark():
+    lic, attr = normalize_license(
+        "https://creativecommons.org/publicdomain/mark/1.0/"
+    )
+    assert lic == "public_domain" and attr == ""
+
+
+def test_no_known_copyright_is_public_domain():
+    lic, attr = normalize_license("No known copyright")
+    assert lic == "public_domain" and attr == ""
+
+
+def test_public_domain_literal():
+    lic, attr = normalize_license("public_domain")
+    assert lic == "public_domain" and attr == ""
+
+
+def test_unmappable_rejected():
+    with pytest.raises(ValueError):
+        normalize_license("All Rights Reserved")
+
+
+def test_empty_rejected():
+    with pytest.raises(ValueError):
+        normalize_license("")
+
+
+def test_librivox_license_helper():
+    lic, attr = librivox_license()
+    assert lic == "public_domain" and attr == ""
+
+
+def test_all_outputs_in_vocab():
+    samples = [
+        "https://creativecommons.org/licenses/by/4.0/",
+        "https://creativecommons.org/licenses/by-nc/4.0/",
+        "CC0",
+        "public domain",
+    ]
+    for raw in samples:
+        lic, _ = normalize_license(raw, creator="x")
+        assert lic in LICENSES