§22 S3: scope-role enforcement + collection-grain visibility (@S3) — v0.42.0

Implement slice S3 of the §22 three-tier refactor: the four-layer
most-permissive scope-role resolver (§B.2) over {owner, contributor}
grants at {global, project, collection}, with the §22.5 visibility gate
enforced at the collection grain.

- migration 030: memberships.scope_type += 'global' (the global RFC
  Contributor tier; sentinel scope_id '*').
- auth.effective_scope_role folds global → project → collection,
  most-permissive, no negative override; can_read_collection /
  can_contribute_in_collection / is_collection_superuser /
  can_create_collection gate reads, writes, admin, and create.
- collection-grain visibility: a gated collection is hidden from the
  public (404, omitted from the directory) yet visible+listed for a
  scope-role holder; a collection may be set only as strict or stricter
  than its project (public < unlisted < gated), validated at create and
  clamped at the mirror.
- entry-scoped authority (mark-reviewed, graduate, branch read/contribute,
  PR/discussion/contribution moderation) re-pointed from the project grain
  to the entry's collection.
- create-collection authority widened to a project/global-scope grant
  holder (§B.1), not only a deployment owner/admin.

Keystone reconciliation (session 0076): a plain granted account is a
granted *account*, not a write-everywhere global role; the implicit-public
write baseline is grandfathered onto the migration-seeded `default`
collection only, so the N=1 deployment loses no capability. Reinterprets
§B.1/§B.3 literally — flagged for the SPEC merge (S6).

Completes @S3 (C1.1–C1.8). Tests: test_s3_scope_roles_vertical.py (8 C.1
scenarios + visibility/strictness), test_migration_030_global_scope.py.
Full backend suite 493 passed.

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

backend/tests/test_migration_030_global_scope.py

@@ -0,0 +1,91 @@
+"""Migration 030 — the global-scope grant (§22 three-tier S3).
+
+Proves: `memberships.scope_type` now admits 'global' alongside 'project' and
+'collection' (§B.2's four-layer resolver), existing rows survive the rebuild,
+and the UNIQUE(scope_type, scope_id, user_id) shape is preserved.
+Template: test_migration_029_collections.py.
+"""
+from __future__ import annotations
+
+import sqlite3
+import tempfile
+from pathlib import Path
+
+import pytest
+
+from app import db
+
+
+class _Cfg:
+    def __init__(self, path):
+        self.database_path = path
+
+
+def _fresh_db():
+    d = tempfile.mkdtemp()
+    path = Path(d) / "t.db"
+    db.run_migrations(_Cfg(str(path)))
+    return db.connect(str(path))
+
+
+def _add_user(conn, uid, login):
+    conn.execute(
+        "INSERT INTO users (id, gitea_id, gitea_login, display_name, role) "
+        "VALUES (?, ?, ?, ?, 'contributor')",
+        (uid, uid, login, login.capitalize()),
+    )
+
+
+def test_global_scope_type_is_accepted():
+    conn = _fresh_db()
+    _add_user(conn, 1, "cleo")
+    # global grant — the new tier — is accepted.
+    conn.execute(
+        "INSERT INTO memberships (scope_type, scope_id, user_id, role) "
+        "VALUES ('global', '*', 1, 'contributor')"
+    )
+    row = conn.execute(
+        "SELECT scope_type, scope_id, role FROM memberships WHERE user_id = 1"
+    ).fetchone()
+    assert row["scope_type"] == "global"
+    assert row["scope_id"] == "*"
+    assert row["role"] == "contributor"
+
+
+def test_project_and_collection_scopes_still_accepted():
+    conn = _fresh_db()
+    _add_user(conn, 1, "ben")
+    conn.execute(
+        "INSERT INTO memberships (scope_type, scope_id, user_id, role) "
+        "VALUES ('project', 'default', 1, 'owner')"
+    )
+    conn.execute(
+        "INSERT INTO memberships (scope_type, scope_id, user_id, role) "
+        "VALUES ('collection', 'default', 1, 'contributor')"
+    )
+    n = conn.execute("SELECT COUNT(*) AS n FROM memberships WHERE user_id = 1").fetchone()["n"]
+    assert n == 2
+
+
+def test_unknown_scope_type_still_rejected():
+    conn = _fresh_db()
+    _add_user(conn, 1, "x")
+    with pytest.raises(sqlite3.IntegrityError):
+        conn.execute(
+            "INSERT INTO memberships (scope_type, scope_id, user_id, role) "
+            "VALUES ('deployment', '*', 1, 'owner')"
+        )
+
+
+def test_one_global_grant_per_user():
+    conn = _fresh_db()
+    _add_user(conn, 1, "cleo")
+    conn.execute(
+        "INSERT INTO memberships (scope_type, scope_id, user_id, role) "
+        "VALUES ('global', '*', 1, 'contributor')"
+    )
+    with pytest.raises(sqlite3.IntegrityError):
+        conn.execute(
+            "INSERT INTO memberships (scope_type, scope_id, user_id, role) "
+            "VALUES ('global', '*', 1, 'owner')"
+        )