F10 #31: render resolved proposals inline at their anchor block

In the F10 review preview, renderReview now emits each pending proposal whose
anchor resolves as a cw-proposal block immediately after the current-side block
its anchorStart falls in — answering "what is Claude proposing, and where?" by
position — instead of appending all proposals as trailing blocks. Proposals in
the same block are ordered by anchorStart then id (deterministic, INV-33); a
proposal whose anchor doesn't resolve (or precedes all blocks) still trails as a
cw-proposal-unanchored block, never dropped (INV-34).

This implements the inline-at-anchor placement the graduated F10 Solution Design
already specified (coauthoring-interactive-review.md §2/§6.2); the trailing-block
behavior shipped in #29 was a recorded v1 deferral.

Unit: mid-document placement, two proposals in distinct blocks, same-block
ordering determinism, anchored-before-trailing, mixed-set determinism.
E2E: the F10 propose test now asserts the proposal renders before the following
block (in place); accept still lands + clears.

194 unit + 51 E2E green; typecheck clean.

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

src/trackChangesModel.ts

@@ -422,8 +422,13 @@ function renderReviewOp(
  * On-state body (INV-33): the F7 baseline diff — added/changed PROSE author-colored
  * via colorByAuthor (F9 sentinels), deletions struck — overlaid with F4 pending
  * proposals as blue cw-proposal blocks (✓/✗). One pass, pure, vscode-free.
- * Resolved proposals append after the diff body; unresolved ones append as trailing
- * cw-proposal-unanchored blocks (never dropped — INV-34).
+ *
+ * A resolved proposal renders INLINE, right after the current-side block its anchor
+ * falls in (#31) — so "what is Claude proposing, and where?" is answered by
+ * position. A proposal whose anchor does not resolve (or falls before the first
+ * block) renders as a trailing cw-proposal-unanchored block (never dropped —
+ * INV-34). Deterministic: proposals in the same block are ordered by anchorStart
+ * then id; trailing proposals keep input order.
  */
 export function renderReview(
   baselineText: string,
@@ -435,17 +440,43 @@ export function renderReview(
   const render = opts.render ?? defaultRender;
   const ranges = splitBlocksWithRanges(currentText);
   const ops = diffBlocks(baselineText, currentText);
+
+  // Associate each resolved proposal with the current-side 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.
+  const blockOf = (a: number): number => {
+    let j = -1;
+    for (let k = 0; k < ranges.length && ranges[k].start <= a; k++) j = k;
+    return j;
+  };
+  const byBlock = new Map<number, ProposalView[]>();
+  const trailing: ProposalView[] = [];
+  for (const p of proposals) {
+    const j = p.anchorStart === null ? -1 : blockOf(p.anchorStart);
+    if (j < 0) {
+      trailing.push(p);
+      continue;
+    }
+    (byBlock.get(j) ?? byBlock.set(j, []).get(j)!).push(p);
+  }
+  for (const arr of byBlock.values()) {
+    arr.sort((a, b) => a.anchorStart! - b.anchorStart! || (a.id < b.id ? -1 : a.id > b.id ? 1 : 0));
+  }
+
   let ci = 0; // pointer into ranges; advances for every op with a current-side block
-  const bodyParts = ops.map((op) => {
+  const bodyParts: string[] = [];
+  for (const op of ops) {
+    const blockIndex = op.kind === "removed" ? -1 : ci;
     const blk = op.kind === "removed" ? undefined : ranges[ci++];
     const colored = (raw: string): string =>
       blk ? colorByAuthor(raw, blk.start, authorSpans, render) : render(raw);
-    return renderReviewOp(op, render, colored);
-  });
-  const anchored = proposals.filter((p) => p.anchorStart !== null);
-  const unanchored = proposals.filter((p) => p.anchorStart === null);
-  const proposalParts = [...anchored, ...unanchored].map((p) => proposalBlockHtml(p, render));
-  return [...bodyParts, ...proposalParts].join("\n");
+    bodyParts.push(renderReviewOp(op, render, colored));
+    const here = blockIndex >= 0 ? byBlock.get(blockIndex) : undefined;
+    if (here) for (const p of here) bodyParts.push(proposalBlockHtml(p, render));
+  }
+  for (const p of trailing) bodyParts.push(proposalBlockHtml(p, render));
+  return bodyParts.join("\n");
 }
 
 /** Pure entry point: annotated HTML body for the preview (INV-22). */