feat(render): INV-50 render-once — diff against current-minus-pending (#64)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/trackChangesModel.test.ts

@@ -375,6 +375,23 @@ describe("renderReview", () => {
     const b = renderReview(doc, doc, [], proposals);
     expect(a).toBe(b);
   });
+
+  test("renderReview renders an applied proposal ONCE, not also as a landed diff (INV-50)", () => {
+    const baseline = "# T\n\nThe brown fox.\n";
+    const current = "# T\n\nThe red fox.\n"; // proposal already optimistically applied
+    const proposals: ProposalView[] = [{
+      id: "pr_1",
+      anchorStart: current.indexOf("The red fox."),
+      anchorEnd: current.indexOf("The red fox.") + "The red fox.".length,
+      replaced: "The brown fox.",      // original
+      replacement: "The red fox.",
+    }];
+    const html = renderReview(baseline, current, [], proposals);
+    // exactly one proposal block
+    expect((html.match(/cw-proposal/g) ?? []).length).toBe(1);
+    // the applied paragraph is NOT also emitted as a word-merged changed block
+    expect(html).not.toContain("<del>brown</del>"); // no double-render of the change as a baseline diff
+  });
 });
 
 import { renderTrackChanges as rtc2 } from "../src/trackChangesModel";