fix(registry): animate mk card offsets with transforms, not top/left

mk-background and mk-clone-wall-transition tween the card's `top`/`left`.
Layout properties snap to integer device pixels, so the move stutters under
the seek-by-frame capture engine (lint: gsap_non_transform_motion). Both
cards sit at top:0/left:0 in CSS, so the values carry straight over to x/y,
and in clone-wall the later scale composes cleanly with the translate.
Re-rendered both and diffed frames against the previous output — identical,
as intended: this changes how the motion is computed, not how it looks.

Adds scripts/lint-registry-items.mjs (bun run lint:registry-items), which
mounts each item into a throwaway project and lints it. Registry items ship
as `<name>.html`, so `hyperframes lint <dir>` fails with "No composition
found" and these items had never actually been linted — which is how both
errors reached main. Verified the script reproduces the original failure on
the pre-fix source.

Left as a local command rather than a CI gate for now; wiring it up needs
two prior fixes, noted in the PR.

package.json

@@ -53,7 +53,8 @@
     "generate:catalog-previews": "tsx scripts/generate-catalog-previews.ts",
     "package:codex-plugin": "node scripts/package-codex-plugin.mjs",
     "upload:docs-images": "bash scripts/upload-docs-images.sh",
-    "prepare": "test -d .git && lefthook install || true"
+    "prepare": "test -d .git && lefthook install || true",
+    "lint:registry-items": "node scripts/lint-registry-items.mjs"
   },
   "devDependencies": {
     "@commitlint/cli": "^20.5.0",

registry/blocks/mk-background/mk-background.html

@@ -189,13 +189,16 @@
           );
         }
 
-        /* bar-mask demo: full-bleed -> rounded card over the stage -> full-bleed */
+        /* bar-mask demo: full-bleed -> rounded card over the stage -> full-bleed.
+           Offset via x/y transforms, not top/left: layout properties snap to
+           integer device pixels and stutter under seek-by-frame capture. The
+           card's CSS base is top:0/left:0, so the transform values match 1:1. */
         if (CONFIG.bar.demo) {
           tl.to(
             card,
             {
-              top: CONFIG.bar.y,
-              left: CONFIG.bar.x,
+              y: CONFIG.bar.y,
+              x: CONFIG.bar.x,
               width: CONFIG.bar.width,
               height: CONFIG.bar.height,
               borderRadius: CONFIG.bar.roundness,
@@ -207,8 +210,8 @@
           tl.to(
             card,
             {
-              top: 0,
-              left: 0,
+              y: 0,
+              x: 0,
               width: W,
               height: H,
               borderRadius: 0,

registry/blocks/mk-clone-wall-transition/mk-clone-wall-transition.html

@@ -182,13 +182,16 @@
         /* The wall sits in place from t=0, fully hidden beneath the
            full-bleed card — the card's shrink IS the wall's reveal. */
 
-        /* 0.2–0.95  outgoing frame shrinks to a rounded card on the wall */
+        /* 0.2–0.95  outgoing frame shrinks to a rounded card on the wall.
+           x/y rather than left/top — layout properties snap to integer device
+           pixels under seek-by-frame capture. Base is top:0/left:0, so the
+           values carry over unchanged, and the later scale composes cleanly. */
         if (CONFIG.card.enabled) {
           tl.to(
             card,
             {
-              top: 330,
-              left: 640,
+              y: 330,
+              x: 640,
               width: 640,
               height: 420,
               borderRadius: 40,

scripts/lint-registry-items.mjs

@@ -0,0 +1,121 @@
+#!/usr/bin/env node
+/**
+ * Lint registry blocks/components the way a user actually receives them.
+ *
+ * `hyperframes lint <dir>` needs an `index.html`, but registry items ship as
+ * `<name>.html`, so pointing the linter at an item directory fails with "No
+ * composition found" — which means registry items were never linted at all.
+ * Two `gsap_non_transform_motion` errors reached main that way.
+ *
+ * This mounts each item into a throwaway project (exactly where `hyperframes
+ * add` would put it) and lints that, reporting only findings for the item's
+ * own file so the host scaffold's noise is ignored.
+ *
+ * Usage:
+ *   node scripts/lint-registry-items.mjs                 # every item
+ *   node scripts/lint-registry-items.mjs mk-background … # named items
+ */
+import {
+  readdirSync,
+  existsSync,
+  mkdtempSync,
+  mkdirSync,
+  copyFileSync,
+  writeFileSync,
+  rmSync,
+} from "node:fs";
+import { join, resolve, dirname } from "node:path";
+import { tmpdir } from "node:os";
+import { fileURLToPath } from "node:url";
+import { spawnSync } from "node:child_process";
+
+const repoRoot = resolve(dirname(fileURLToPath(import.meta.url)), "..");
+const cli = join(repoRoot, "packages/cli/src/cli.ts");
+
+// A deliberately boring host: one clip, one registered timeline, so the only
+// findings that can appear are the item's own.
+const HOST = `<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=1920, height=1080" />
+    <script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
+  </head>
+  <body>
+    <div id="root" data-composition-id="main" data-start="0" data-width="1920" data-height="1080" data-duration="5">
+      <section id="host-slot" class="clip" data-start="0" data-duration="5" data-track-index="1"></section>
+    </div>
+    <script>
+      window.__timelines = window.__timelines || {};
+      const tl = gsap.timeline({ paused: true });
+      tl.to("#host-slot", { opacity: 1, duration: 0.1 }, 0);
+      window.__timelines["main"] = tl;
+    </script>
+  </body>
+</html>
+`;
+
+/**
+ * Rules that assume a standalone composition. Many components ship as
+ * paste-able fragments with no root element at all, so these fire on ~47
+ * long-standing items and would drown the signal. The host provides the root;
+ * the item is not supposed to.
+ */
+const IGNORED = [
+  "root_missing_composition_id",
+  "root_missing_dimensions",
+  "multiple_root_compositions",
+];
+
+function discover() {
+  const out = [];
+  for (const kind of ["blocks", "components"]) {
+    const dir = join(repoRoot, "registry", kind);
+    if (!existsSync(dir)) continue;
+    for (const name of readdirSync(dir)) {
+      const html = join(dir, name, `${name}.html`);
+      if (existsSync(html)) out.push({ name, kind, html });
+    }
+  }
+  return out;
+}
+
+const only = process.argv.slice(2);
+const items = discover().filter((i) => only.length === 0 || only.includes(i.name));
+if (items.length === 0) {
+  console.error(
+    only.length ? `No registry item matches: ${only.join(", ")}` : "No registry items found.",
+  );
+  process.exit(1);
+}
+
+let failed = 0;
+for (const item of items) {
+  const proj = mkdtempSync(join(tmpdir(), `hf-lint-${item.name}-`));
+  try {
+    mkdirSync(join(proj, "compositions"), { recursive: true });
+    writeFileSync(join(proj, "index.html"), HOST);
+    copyFileSync(item.html, join(proj, "compositions", `${item.name}.html`));
+
+    const res = spawnSync("bun", [cli, "lint", proj], { encoding: "utf-8" });
+    const lines = `${res.stdout ?? ""}${res.stderr ?? ""}`.split("\n");
+    // Only the item's own file — the host scaffold is not under review.
+    const hits = lines.filter(
+      (l) =>
+        l.includes("✗") && l.includes(`${item.name}.html`) && !IGNORED.some((r) => l.includes(r)),
+    );
+    if (hits.length) {
+      failed++;
+      console.error(`\n✗ ${item.kind}/${item.name}`);
+      for (const h of hits) console.error(`   ${h.trim()}`);
+    }
+  } finally {
+    rmSync(proj, { recursive: true, force: true });
+  }
+}
+
+if (failed) {
+  console.error(`\n${failed} registry item(s) have lint errors.`);
+  process.exit(1);
+}
+console.log(`Registry item lint passed — ${items.length} item(s), 0 errors.`);