feat: currentAuthor() carries git user.email — fail-open identity (F5 SLICE-2, #14)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/threadController.ts

@@ -11,6 +11,7 @@ import * as vscode from "vscode";
 import { CoauthorStore } from "./store";
 import { emptyArtifact, type Artifact, type Provenance } from "./model";
 import { buildFingerprint, resolve, shift, type OffsetRange } from "./anchorer";
+import { gitUserEmail } from "./identity";
 import { addThread, appendMessage, setStatus } from "./threadModel";
 
 /** Test-facing snapshot of what is currently rendered for a document. */
@@ -72,7 +73,8 @@ export class ThreadController implements vscode.Disposable {
 
   private currentAuthor(): Provenance {
     const id = vscode.workspace.getConfiguration("git").get<string>("user.name") || process.env.USER || "human";
-    return { kind: "human", id };
+    const email = gitUserEmail(this.rootDir);
+    return { kind: "human", id, ...(email !== undefined ? { email } : {}) };
   }
 
   private persist(state: DocState): void {