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

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

src/trackChangesModel.ts

@@ -793,8 +793,22 @@ export function renderReview(
   opts: RenderOptions = {},
 ): string {
   const render = opts.render ?? defaultRender;
-  const ranges = splitBlocksWithRanges(currentText);
-  const ops = diffBlocks(baselineText, currentText);
+
+  // F12/#64 (INV-50): with optimistic apply the proposed text is already in
+  // `currentText`, so a naive baseline→current diff would render each proposed
+  // change BOTH as a landed diff and as its proposal block. Diff against
+  // `currentText` with every resolved pending proposal reverted to its original,
+  // so the landed diff excludes pending proposals; they render once, as proposals.
+  const pendingApplied = proposals
+    .filter((p) => p.anchorStart !== null)
+    .sort((a, b) => b.anchorStart! - a.anchorStart!);
+  let landedText = currentText;
+  for (const p of pendingApplied) {
+    landedText = landedText.slice(0, p.anchorStart!) + p.replaced + landedText.slice(p.anchorEnd!);
+  }
+
+  const ranges = splitBlocksWithRanges(landedText);
+  const ops = diffBlocks(baselineText, landedText);
   // #48: right after a PIN (baseline reason "pinned") with no changes since, the
   // panel is fully clean: no change marks (already absent) AND no authorship
   // coloring, so the pin reads as "this is my clean starting point". Skip
@@ -804,7 +818,17 @@ export function renderReview(
   // its authorship coloring (F10 INV-33), so this is gated on the pin specifically.
   const clean = opts.pinned === true && ops.every((o) => o.kind === "unchanged");
 
-  // Associate each resolved proposal with the current-side block index whose range
+  // Map a currentText offset to its landedText offset (account for reverted spans
+  // that precede it; reverts were applied high→low so the cumulative delta is stable).
+  const toLanded = (curOff: number): number => {
+    let delta = 0;
+    for (const p of [...pendingApplied].sort((a, b) => a.anchorStart! - b.anchorStart!)) {
+      if (p.anchorStart! < curOff) delta += p.replaced.length - (p.anchorEnd! - p.anchorStart!);
+    }
+    return curOff + delta;
+  };
+
+  // Associate each resolved proposal with the landedText block index whose range
   // it anchors into: the largest block with start <= anchorStart (the containing
   // block, or the nearest preceding block when the anchor sits in a gap). A
   // resolved anchor before all blocks, and every unresolved proposal, trails.
@@ -816,7 +840,7 @@ export function renderReview(
   const byBlock = new Map<number, ProposalView[]>();
   const trailing: ProposalView[] = [];
   for (const p of proposals) {
-    const j = p.anchorStart === null ? -1 : blockOf(p.anchorStart);
+    const j = p.anchorStart === null ? -1 : blockOf(toLanded(p.anchorStart));
     if (j < 0) {
       trailing.push(p);
       continue;