Introduce oauth2scope registry with freeze lifecycle

Replace pkg/iam/scopeset with pkg/iam/oauth2scope.Registry, a shared
OAuth2 scope→action registry used by the authorizer, OAuth2 service,
and Connect API. Registration stays open until probod calls Freeze();
read paths (RegisteredScopes, Allows, ValidateScopes) panic before
that.

Drop the leaky APIScopes surface and AllowedAPIScopes on manual
access-token creation in favor of registry.ValidateScopes. Metadata,
protected-resource metadata, and CIMD scope lists are built from
RegisteredScopes() via helpers in pkg/iam/oauth2/scopes.go. Expose
oauth2ScopesSupported as an OAuth2Scope GraphQL scalar.

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

pkg/iam/oauth2scope/registry_test.go

@@ -0,0 +1,105 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package oauth2scope_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.probo.inc/probo/pkg/coredata"
+	"go.probo.inc/probo/pkg/iam/oauth2scope"
+)
+
+func TestRegistry_Allows(t *testing.T) {
+	t.Parallel()
+
+	const scopeV1OrgRead = coredata.OAuth2Scope("v1:org:read")
+
+	reg := oauth2scope.NewRegistry().Register(
+		map[coredata.OAuth2Scope][]string{
+			scopeV1OrgRead: {"core:organization:get"},
+		},
+	)
+
+	tokenScopes := coredata.OAuth2Scopes{scopeV1OrgRead}
+
+	assert.True(t, reg.Allows(tokenScopes, "core:organization:get"))
+	assert.False(t, reg.Allows(tokenScopes, "core:organization:update"))
+}
+
+func TestRegistry_Register(t *testing.T) {
+	t.Parallel()
+
+	const scopeV1OrgRead = coredata.OAuth2Scope("v1:org:read")
+
+	reg := oauth2scope.NewRegistry().
+		Register(
+			map[coredata.OAuth2Scope][]string{
+				scopeV1OrgRead: {"core:organization:get"},
+			},
+		).
+		Register(
+			map[coredata.OAuth2Scope][]string{
+				scopeV1OrgRead: {"core:organization-context:get"},
+			},
+		)
+
+	tokenScopes := coredata.OAuth2Scopes{scopeV1OrgRead}
+
+	assert.True(t, reg.Allows(tokenScopes, "core:organization:get"))
+	assert.True(t, reg.Allows(tokenScopes, "core:organization-context:get"))
+}
+
+func TestRegistry_ValidateScopes(t *testing.T) {
+	t.Parallel()
+
+	const scopeV1OrgRead = coredata.OAuth2Scope("v1:org:read")
+
+	reg := oauth2scope.NewRegistry().Register(
+		map[coredata.OAuth2Scope][]string{
+			scopeV1OrgRead: {"core:organization:get"},
+		},
+	)
+
+	require.NoError(t, reg.ValidateScopes(coredata.OAuth2Scopes{scopeV1OrgRead}))
+
+	err := reg.ValidateScopes(coredata.OAuth2Scopes{"v1:unknown:read"})
+	require.Error(t, err)
+	assert.EqualError(t, err, "invalid scope: v1:unknown:read")
+}
+
+func TestRegistry_RegisteredScopes(t *testing.T) {
+	t.Parallel()
+
+	const (
+		scopeV1OrgRead  = coredata.OAuth2Scope("v1:org:read")
+		scopeV1OrgWrite = coredata.OAuth2Scope("v1:org")
+	)
+
+	reg := oauth2scope.NewRegistry().
+		Register(
+			map[coredata.OAuth2Scope][]string{
+				scopeV1OrgWrite: {"core:organization:update"},
+				scopeV1OrgRead:  {"core:organization:get"},
+			},
+		)
+
+	assert.Equal(
+		t,
+		[]coredata.OAuth2Scope{scopeV1OrgWrite, scopeV1OrgRead},
+		reg.RegisteredScopes(),
+	)
+}