diigo-cache: own test toolchain; pnpm lint, pnpm test

vitest, @cloudflare/vitest-plugin, and typescript are devDependencies
here instead of being borrowed from diigo-bookmarks through hand-made
node_modules symlinks and a deep-path import.

- lint: wrangler types, then tsc over src/ and tests/ (Cloudflare's
  documented typecheck shape: regenerate types, then tsc)
- test: vitest run
- tests/tsconfig.json per the vitest-plugin docs; the dangling
  typecheck script (tsconfig.check.json never existed) is gone

Generated-by: Claude Opus 5.5

diigo-cache/vitest.config.ts

@@ -1,9 +1,5 @@
 import { defineProject } from "vitest/config";
-// the plugin resolves from diigo-bookmarks's store (the one vitest
-// install on disk); direct-path import sidesteps pnpm's exports-map
-// restriction *for the config file*. cloudflareTest (the plugin form,
-// not the bare pool) is what provides the `cloudflare:test` module.
-import { cloudflareTest } from "../diigo-bookmarks/node_modules/.pnpm/@cloudflare+vitest-plugin@1.3.6_@cloudflare+workers-types@5.20261005.1_@types+node@26.6.4_@vi_7mty7nznaeeyt2ohspxbzj4p6m/node_modules/@cloudflare/vitest-plugin/dist/pool/index.mjs";
+import { cloudflareTest } from "@cloudflare/vitest-plugin";
 
 export default defineProject({
 	plugins: [