fix: final-review findings (median pass tick, R11 secondary metrics, R12 chord duration, render version, dsp resample)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/bench/dataset.test.ts

@@ -2,7 +2,7 @@ import { test, expect } from "bun:test";
 import { mkdtemp, rm } from "node:fs/promises";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import { buildSong, loadSongDir } from "../../src/bench/dataset.ts";
+import { buildSong, loadSongDir, RENDER_VERSION } from "../../src/bench/dataset.ts";
 
 test("buildSong writes all artefacts; loadSongDir reads them; stems sum to mix; idempotent", async () => {
   const root = await mkdtemp(join(tmpdir(), "stsheets-ds-"));
@@ -55,3 +55,27 @@ test("multi-track t1b: stems on disk sum to mix.wav", async () => {
     await rm(root, { recursive: true, force: true });
   }
 }, 120_000);
+
+test("a dir built under an older/missing RENDER_VERSION is rebuilt", async () => {
+  const root = await mkdtemp(join(tmpdir(), "stsheets-ds-"));
+  try {
+    const dir = await buildSong("t1a", 2, root);
+    const mp3 = join(dir, "mix.mp3");
+    const v = Bun.file(join(dir, "render-version"));
+    expect((await v.text()).trim()).toBe(String(RENDER_VERSION));
+    const m0 = (await Bun.file(mp3).stat()).mtimeMs;
+    await Bun.write(join(dir, "render-version"), String(RENDER_VERSION - 1)); // simulate an old build
+    await Bun.sleep(20);
+    await buildSong("t1a", 2, root);
+    const m1 = (await Bun.file(mp3).stat()).mtimeMs;
+    expect(m1).toBeGreaterThan(m0);
+    expect((await Bun.file(join(dir, "render-version")).text()).trim()).toBe(String(RENDER_VERSION));
+    // missing marker file also rebuilds
+    await rm(join(dir, "render-version"));
+    await Bun.sleep(20);
+    await buildSong("t1a", 2, root);
+    expect((await Bun.file(mp3).stat()).mtimeMs).toBeGreaterThan(m1);
+  } finally {
+    await rm(root, { recursive: true, force: true });
+  }
+}, 180_000);