fix(collab): dedupe yjs so @pcbjam/shared + standalone link ONE instance

Two pnpm workspaces (root globs pcbjam-shared; pcbjam/web has it too) each install yjs, so shared's collab code (kicad-y) and the app's yjs were two physical copies → a Y.Map rejects the other instance's Y types ('Unexpected content type'). resolve.dedupe:['yjs'] in vite + vitest forces a single copy. Not a test-only artifact: the same two copies bundle into the editor and would break collab on doc seed. Full standalone suite now 55/55 (was 47/55).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/standalone/vitest.config.ts

@@ -7,6 +7,11 @@ import { defineConfig } from "vitest/config";
 export default defineConfig({
   resolve: {
     alias: { "@": path.resolve(__dirname, "./src") },
+    // @pcbjam/shared lives in a second pnpm workspace, so without this its `yjs`
+    // and the standalone's `yjs` resolve to two physical copies → a Y.Map from
+    // one instance rejects Y types from the other ("Unexpected content type").
+    // Force a single yjs (it's a shared mutable singleton — instanceof-checked).
+    dedupe: ["yjs"],
   },
   test: {
     environment: "node",