Add multi-account OAuth, Obsidian integration, product assets, and test tooling

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

product/site/compare-screenshot.mjs

@@ -0,0 +1,53 @@
+import fs from "fs";
+import { PNG } from "pngjs";
+import pixelmatch from "pixelmatch";
+
+const actualPath = process.argv[2];
+const baselinePath = process.argv[3];
+const diffPath = process.argv[4] || "/tmp/squaremcp-visual-diff.png";
+const threshold = Number(process.argv[5] || "0.02");
+const maxDiffRatio = Number(process.argv[6] || "0.01");
+
+if (!actualPath || !baselinePath) {
+  console.error("usage: node compare-screenshot.mjs <actual> <baseline> [diff] [threshold] [maxDiffRatio]");
+  process.exit(1);
+}
+
+if (!fs.existsSync(actualPath) || !fs.existsSync(baselinePath)) {
+  console.error("actual or baseline screenshot is missing");
+  process.exit(1);
+}
+
+const actual = PNG.sync.read(fs.readFileSync(actualPath));
+const baseline = PNG.sync.read(fs.readFileSync(baselinePath));
+
+if (actual.width !== baseline.width || actual.height !== baseline.height) {
+  console.error(
+    `dimension mismatch: actual ${actual.width}x${actual.height}, baseline ${baseline.width}x${baseline.height}`
+  );
+  process.exit(1);
+}
+
+const diff = new PNG({ width: actual.width, height: actual.height });
+const mismatchedPixels = pixelmatch(
+  actual.data,
+  baseline.data,
+  diff.data,
+  actual.width,
+  actual.height,
+  { threshold }
+);
+
+const diffRatio = mismatchedPixels / (actual.width * actual.height);
+fs.writeFileSync(diffPath, PNG.sync.write(diff));
+
+if (diffRatio > maxDiffRatio) {
+  console.error(
+    `visual diff exceeded threshold: mismatched=${mismatchedPixels} ratio=${diffRatio.toFixed(6)} diff=${diffPath}`
+  );
+  process.exit(1);
+}
+
+console.log(
+  `visual diff PASS: mismatched=${mismatchedPixels} ratio=${diffRatio.toFixed(6)} diff=${diffPath}`
+);