F3 SLICE-1: typed attributions[] model (spec §6.3, INV-4) (#6)

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

src/model.ts

@@ -47,6 +47,20 @@ export interface Thread {
   messages: Message[];
 }
 
+/** F3 (spec §6.3): an anchored, author-attributed span — state, not history. */
+export interface AttributionRecord {
+  id: string;
+  /** shared anchors map — same Fingerprint primitive (INV-4). */
+  anchorId: string;
+  author: Provenance;
+  /** ISO-8601. */
+  createdAt: string;
+  /** ISO-8601; bumped when the span's extent/fingerprint changes. */
+  updatedAt: string;
+  /** groups all spans applied by one live turn. */
+  turnId?: string;
+}
+
 export interface Artifact {
   schemaVersion: number;
   /** repo-relative path; the sidecar key. */
@@ -54,8 +68,8 @@ export interface Artifact {
   /** SHARED primitive (INV-4). */
   anchors: Record<string, Anchor>;
   threads: Thread[];
-  /** F3 extension point — reuses anchors[]; not implemented in F2. */
-  attributions: unknown[];
+  /** F3 fills this (spec §6.3, INV-4): typed attribution records anchored via anchors[]. */
+  attributions: AttributionRecord[];
   /** F4 extension point — reuses anchors[] + provenance; not in F2. */
   proposals: unknown[];
 }
@@ -117,7 +131,14 @@ export function serializeArtifact(a: Artifact): string {
         createdAt: m.createdAt,
       })),
     })),
-    attributions: a.attributions,
+    attributions: a.attributions.map((at) => ({
+      id: at.id,
+      anchorId: at.anchorId,
+      author: serializeProvenance(at.author),
+      createdAt: at.createdAt,
+      updatedAt: at.updatedAt,
+      ...(at.turnId !== undefined ? { turnId: at.turnId } : {}),
+    })),
     proposals: a.proposals,
   };
   return JSON.stringify(canonical, null, 2) + "\n";