fix(css,preview): scope utilities under the view root, preview with real boards and foreign css

tests/scope-css.test.ts

@@ -0,0 +1,63 @@
+import { describe, expect, it } from "vitest";
+import { scopeCss } from "../scripts/scope-css.mjs";
+
+const one = (css: string) => scopeCss(css).replace(/\s+/gu, " ").trim();
+
+describe("scoping the built stylesheet", () => {
+  it("prefixes a utility with the view root, keeping the root itself in reach", () => {
+    expect(one(".flex{display:flex!important}")).toBe(
+      ":is(.bcal-root, .bcal-root *).flex { display: flex !important; }",
+    );
+  });
+
+  it("outranks the same utility from another plugin's Tailwind", () => {
+    // Class specificity: theirs is (0,1,0); ours must be (0,2,0).
+    const out = one(".hidden{display:none!important}");
+    expect(out.startsWith(":is(.bcal-root, .bcal-root *).hidden")).toBe(true);
+  });
+
+  it("keeps pseudo-elements at the end where they are valid", () => {
+    expect(one(".x::placeholder{color:red}")).toBe(
+      ":is(.bcal-root, .bcal-root *).x::placeholder { color: red; }",
+    );
+    expect(one(".y::first-letter{t:1}")).toContain(".y:first-letter");
+  });
+
+  it("scopes rules nested in container queries and layers", () => {
+    const out = one(
+      "@layer utilities{@container (min-width:30rem){.a{display:inline-block!important}}}",
+    );
+    // lightningcss rewrites the query into range syntax; Obsidian's Chromium
+    // has understood that inside @container since container queries landed.
+    expect(out).toContain("@container (width >= 30rem)");
+    expect(out).toContain(":is(.bcal-root, .bcal-root *).a");
+  });
+
+  it("drops a leading universal selector instead of producing `:is()*`", () => {
+    const out = one("*,:before,::backdrop{--tw-a:initial}");
+    expect(out).toContain(":is(.bcal-root, .bcal-root *),");
+    expect(out).toContain(":is(.bcal-root, .bcal-root *):before");
+    expect(out).not.toContain("*)*");
+  });
+
+  it("moves theme variables from :root onto the view root", () => {
+    expect(one(":root,:host{--spacing:.25rem}")).toBe(
+      ".bcal-root { --spacing: .25rem; }",
+    );
+  });
+
+  it("leaves rules that already name the root alone", () => {
+    const reset = ".bcal-root.bcal-root button{cursor:pointer}";
+    expect(one(reset)).toBe(".bcal-root.bcal-root button { cursor: pointer; }");
+    expect(one(".theme-dark .bcal-root{--note:red}")).toBe(
+      ".theme-dark .bcal-root { --note: red; }",
+    );
+  });
+
+  it("scopes variant selectors without breaking their inner :where()", () => {
+    const out = one(".dark\\:bg-x:where(.theme-dark,.theme-dark *){b:1}");
+    expect(out).toBe(
+      ":is(.bcal-root, .bcal-root *).dark\\:bg-x:where(.theme-dark, .theme-dark *) { b: 1; }",
+    );
+  });
+});