F3 SLICE-3: pending-edit registry + sidecar section-merge update (INV-9 groundwork) (#6)

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

src/pendingEdits.ts

@@ -0,0 +1,48 @@
+/**
+ * PendingEditRegistry — the seam's bookkeeping (spec §6.2, INV-9). Before
+ * applyAgentEdit applies a WorkspaceEdit, it registers the exact expected
+ * change; the controller's change handler consumes a matching registration to
+ * attribute that change to the agent. Anything unmatched is human typing.
+ * vscode-free and unit-testable.
+ */
+import type { Provenance } from "./model";
+
+export interface PendingEdit {
+  docPath: string;
+  /** half-open [start, end) offsets of the replaced range. */
+  start: number;
+  end: number;
+  newText: string;
+  provenance: Provenance;
+  turnId?: string;
+}
+
+export class PendingEditRegistry {
+  private pending: PendingEdit[] = [];
+
+  register(edit: PendingEdit): void {
+    this.pending.push(edit);
+  }
+
+  /** Remove a registration that failed to apply. */
+  unregister(edit: PendingEdit): void {
+    this.pending = this.pending.filter((p) => p !== edit);
+  }
+
+  /**
+   * Find-and-consume the registration exactly matching a change event
+   * (same doc, same replaced range, same inserted text). Null → human edit.
+   */
+  match(docPath: string, change: { start: number; end: number; text: string }): PendingEdit | null {
+    const i = this.pending.findIndex(
+      (p) =>
+        p.docPath === docPath &&
+        p.start === change.start &&
+        p.end === change.end &&
+        p.newText === change.text,
+    );
+    if (i === -1) return null;
+    const [hit] = this.pending.splice(i, 1);
+    return hit;
+  }
+}

src/store.ts

@@ -6,7 +6,7 @@
  */
 import * as fs from "node:fs";
 import * as path from "node:path";
-import { serializeArtifact, type Artifact } from "./model";
+import { emptyArtifact, serializeArtifact, type Artifact } from "./model";
 
 export class CoauthorStore {
   /** @param rootDir absolute workspace-folder root that owns the `.threads/` tree. */
@@ -28,4 +28,25 @@ export class CoauthorStore {
     fs.mkdirSync(path.dirname(p), { recursive: true });
     fs.writeFileSync(p, serializeArtifact(artifact), "utf8");
   }
+
+  /**
+   * Read-modify-write for sidecar co-ownership (spec F3 §6.2): each controller
+   * 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).
+   */
+  update(docPath: string, mutate: (artifact: Artifact) => void): Artifact {
+    const artifact = this.load(docPath) ?? emptyArtifact(docPath);
+    mutate(artifact);
+    const referenced = new Set<string>([
+      ...artifact.threads.map((t) => t.anchorId),
+      ...artifact.attributions.map((a) => a.anchorId),
+    ]);
+    for (const id of Object.keys(artifact.anchors)) {
+      if (!referenced.has(id)) delete artifact.anchors[id];
+    }
+    this.save(docPath, artifact);
+    return artifact;
+  }
 }

src/threadController.ts

@@ -84,7 +84,12 @@ export class ThreadController implements vscode.Disposable {
 
   private persist(state: DocState): void {
     this.selfWrites.add(this.store.sidecarPath(state.docPath));
-    this.store.save(state.docPath, state.artifact);
+    this.store.update(state.docPath, (a) => {
+      a.threads = state.artifact.threads;
+      for (const t of state.artifact.threads) {
+        a.anchors[t.anchorId] = state.artifact.anchors[t.anchorId];
+      }
+    });
   }
 
   private ensureState(document: vscode.TextDocument): DocState {