Restructure solution layout by module

src/Policy/__Libraries/StellaOps.Policy/PolicyPreviewModels.cs

@@ -0,0 +1,18 @@
+using System.Collections.Immutable;
+
+namespace StellaOps.Policy;
+
+public sealed record PolicyPreviewRequest(
+    string ImageDigest,
+    ImmutableArray<PolicyFinding> Findings,
+    ImmutableArray<PolicyVerdict> BaselineVerdicts,
+    PolicySnapshot? SnapshotOverride = null,
+    PolicySnapshotContent? ProposedPolicy = null);
+
+public sealed record PolicyPreviewResponse(
+    bool Success,
+    string PolicyDigest,
+    string? RevisionId,
+    ImmutableArray<PolicyIssue> Issues,
+    ImmutableArray<PolicyVerdictDiff> Diffs,
+    int ChangedCount);