F3 SLICE-3: applyAgentEdit seam + live tracking + decorations/toggle (INV-7/INV-9) (#6)

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

src/store.ts

@@ -1,17 +1,31 @@
 /**
  * CoauthorStore — load/save the per-document `.threads/` sidecar (spec §6.4).
  * Git-native, serverless, plain pretty JSON (INV-2). vscode-free (Node fs only),
- * so it is unit-testable; the FileSystemWatcher that triggers re-anchoring on
- * external change is wired in the vscode layer (ThreadController, SLICE-4).
+ * so it is unit-testable; the SHARED FileSystemWatcher that triggers
+ * re-anchoring on external change is wired in the vscode layer (extension.ts),
+ * with self-write suppression centralized here because two controllers
+ * (ThreadController, AttributionController) co-own the sidecar (F3 §6.2).
  */
 import * as fs from "node:fs";
 import * as path from "node:path";
 import { emptyArtifact, serializeArtifact, type Artifact } from "./model";
 
 export class CoauthorStore {
+  /** sidecar paths this store just wrote, so the shared watcher can ignore them. */
+  private readonly selfWrites = new Set<string>();
+
   /** @param rootDir absolute workspace-folder root that owns the `.threads/` tree. */
   constructor(private readonly rootDir: string) {}
 
+  /**
+   * Delete-and-report: true iff `fsPath` was a sidecar we just wrote via
+   * `update`. The shared watcher (extension.ts) calls this to suppress
+   * self-write events before fanning out to the controllers.
+   */
+  consumeSelfWrite(fsPath: string): boolean {
+    return this.selfWrites.delete(fsPath);
+  }
+
   /** `.threads/<repo-relative-docPath>.json` (spec §6.3). */
   sidecarPath(docPath: string): string {
     return path.join(this.rootDir, ".threads", `${docPath}.json`);
@@ -34,7 +48,8 @@ export class CoauthorStore {
    * mutates only its own section against a FRESH load, so ThreadController and
    * AttributionController never clobber each other. After the mutation, anchors
    * referenced by neither threads nor attributions are pruned (proposals are
-   * still empty in F3 — revisit in F4).
+   * still empty in F3 — revisit in F4). `mutate` MUST be synchronous: the
+   * read-modify-write (and the self-write mark) completes within this call.
    */
   update(docPath: string, mutate: (artifact: Artifact) => void): Artifact {
     const artifact = this.load(docPath) ?? emptyArtifact(docPath);
@@ -46,6 +61,7 @@ export class CoauthorStore {
     for (const id of Object.keys(artifact.anchors)) {
       if (!referenced.has(id)) delete artifact.anchors[id];
     }
+    this.selfWrites.add(this.sidecarPath(docPath));
     this.save(docPath, artifact);
     return artifact;
   }