#48: pinning the baseline leaves the review panel fully un-annotated

A pinned baseline with no changes since should read as a clean starting point,
but the F10 on-render still author-colored every block (colorByAuthor), painting
the whole document green/blue right after a pin. Now, when the baseline reason is
"pinned" and there are zero changes since (every diffBlocks op unchanged), the
on-render is fully clean — no change marks and no authorship coloring — while the
data-src block mapping (INV-36) and any pending proposals (review actions, not
annotations) are kept.

Scoped to the PIN specifically, not all zero-diff: a baseline advanced by a
machine-landing (accept) is also zero-diff but keeps its authorship coloring so
accepted Claude text stays blue (F10 INV-33). renderReview takes a `pinned`
option; the controller passes baseline.reason === "pinned" from both refresh and
the renderHtmlFor test seam.

- trackChangesModel.ts: renderReview gains the `pinned` RenderOption; when pinned
  + zero-diff, blocks render plain (no colorByAuthor).
- trackChangesPreview.ts: pass { pinned } through refresh + renderHtmlFor.
- unit: pinned+zero-diff → no cw-by-*; pinned+zero-diff still shows proposals;
  zero-diff WITHOUT pin (machine-landing) keeps coloring (INV-33); real changes
  after a pin re-color.
- s48PinClean host E2E: type → colored; pin → clean; edit → annotations return.

218 unit + 74/5 host E2E green.

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

src/trackChangesModel.ts

@@ -441,6 +441,14 @@ function wordMergedMarkdown(beforeRaw: string, afterRaw: string): string {
 export interface RenderOptions {
   /** Per-block markdown→HTML renderer (test seam). Defaults to the bundled markdown-it. */
   render?: (src: string) => string;
+  /**
+   * #48: the baseline was just PINNED (`reason === "pinned"`). With zero changes
+   * since that pin, the on-render is fully clean — no authorship coloring — so a
+   * pin reads as "this is my clean starting point". Distinct from a baseline
+   * advanced by a machine-landing (accept), which keeps its authorship coloring
+   * (F10 INV-33). Only consulted by `renderReview`.
+   */
+  pinned?: boolean;
 }
 
 function defaultRender(src: string): string {
@@ -673,6 +681,14 @@ export function renderReview(
   const render = opts.render ?? defaultRender;
   const ranges = splitBlocksWithRanges(currentText);
   const ops = diffBlocks(baselineText, currentText);
+  // #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
+  // colorByAuthor for every block in this case; data-src mapping and any pending
+  // proposals (review actions, not annotations) are kept below. A baseline advanced
+  // by a machine-landing (accept) is ALSO zero-diff but is NOT pinned — it keeps
+  // 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
   // it anchors into: the largest block with start <= anchorStart (the containing
@@ -703,7 +719,7 @@ export function renderReview(
     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);
+      blk && !clean ? colorByAuthor(raw, blk.start, authorSpans, render) : render(raw);
     bodyParts.push(renderReviewOp(op, render, colored, srcAttr(blk)));
     const here = blockIndex >= 0 ? byBlock.get(blockIndex) : undefined;
     if (here) for (const p of here) bodyParts.push(proposalBlockHtml(p, render));