#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>

test/e2e/suite/s48PinClean.test.ts

@@ -0,0 +1,63 @@
+import * as assert from "assert";
+import * as fs from "fs";
+import * as path from "path";
+import * as vscode from "vscode";
+import type { CowritingApi } from "../../../src/extension";
+
+const WS = process.env.E2E_WORKSPACE!;
+const settle = () => new Promise((r) => setTimeout(r, 400));
+
+async function getApi(): Promise<CowritingApi> {
+  const ext = vscode.extensions.getExtension("benstull.vscode-cowriting-plugin")!;
+  const api = (await ext.activate()) as CowritingApi;
+  assert.ok(api?.trackChangesPreviewController, "exports preview controller");
+  return api;
+}
+
+async function freshDoc(rel: string, body: string): Promise<{ doc: vscode.TextDocument; key: string }> {
+  const abs = path.join(WS, rel);
+  fs.mkdirSync(path.dirname(abs), { recursive: true });
+  fs.writeFileSync(abs, body, "utf8");
+  const uri = vscode.Uri.file(abs);
+  const doc = await vscode.workspace.openTextDocument(uri);
+  await vscode.window.showTextDocument(doc);
+  await settle();
+  return { doc, key: uri.toString() };
+}
+
+// #48 host E2E (no LLM): pinning the baseline leaves the review panel fully clean
+// — no authorship coloring on unchanged blocks — while re-divergence brings the
+// annotations back. The author colors are read from the on-state renderReview HTML.
+suite("S48 — pin → fully clean review panel (host E2E, no LLM)", () => {
+  test("pin clears authorship coloring; a later edit brings annotations back", async () => {
+    const { doc, key } = await freshDoc("docs/s48pin.md", "# S48\n\nAn original baseline paragraph.\n");
+    const api = await getApi();
+    const ctl = api.trackChangesPreviewController;
+    await vscode.commands.executeCommand("cowriting.showTrackChangesPreview");
+    await settle();
+
+    // Type a paragraph → a human attribution span + author coloring in the on-state.
+    const edit = new vscode.WorkspaceEdit();
+    edit.insert(doc.uri, doc.positionAt(doc.getText().length), "\n\nA freshly typed human paragraph.\n");
+    assert.ok(await vscode.workspace.applyEdit(edit), "operator edit applied");
+    await settle();
+    assert.match(ctl.renderHtmlFor(key), /cw-by-human/, "typed text is author-colored before the pin");
+
+    // Pin the baseline → zero diff → the panel must be fully clean.
+    ctl.receiveMessage(key, { type: "pinBaseline" });
+    await settle();
+    const pinned = ctl.renderHtmlFor(key);
+    assert.ok(!pinned.includes("cw-by-human"), "no human authorship coloring after pin");
+    assert.ok(!pinned.includes("cw-by-claude"), "no Claude authorship coloring after pin");
+    assert.ok(!pinned.includes("cw-add") && !pinned.includes("cw-del"), "no change marks after pin");
+    assert.match(pinned, /data-src-start/, "blocks still carry data-src offsets (INV-36 mapping kept)");
+    assert.ok(pinned.includes("freshly typed human paragraph"), "the body text is still rendered, just plain");
+
+    // Edit again → there are changes since the pinned baseline → annotations return.
+    const edit2 = new vscode.WorkspaceEdit();
+    edit2.insert(doc.uri, doc.positionAt(doc.getText().length), "\n\nA second typed paragraph diverges again.\n");
+    assert.ok(await vscode.workspace.applyEdit(edit2), "second operator edit applied");
+    await settle();
+    assert.match(ctl.renderHtmlFor(key), /cw-by-human/, "authorship coloring returns once the doc diverges from the pin");
+  });
+});