fix: use a relative tsconfig root for the TypeScript checker

[Artur-]

vite-plugin-checker builds the tsc command line as a string and splits it on spaces, so the absolute "-p " argument breaks type checking when the project directory contains a space. Vite is always started with the project root as its working directory, both for the production build and for the dev server, so a relative "." resolves to the same tsconfig.json without introducing a splittable argument.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Test Results

 1 450 files  ±0   1 451 suites  ±0   1h 29m 11s ⏱️ + 3m 21s
10 409 tests ±0  10 342 ✅ ±0  67 💤 ±0  0 ❌ ±0 
10 845 runs  ±0  10 777 ✅ ±0  68 💤 ±0  0 ❌ ±0 

Results for commit d099503. ± Comparison against base commit 63992ea.

[Dudeplayz]

Cross-reference: this change has a side effect that looks unintended — see vaadin/hilla#6040 for the full context.

vite-plugin-checker resolves the project-local TypeScript by handing its root option to createRequire:

// vite-plugin-checker@0.14.5/dist/checkers/typescript/main.js
try {
  const tsEntry = createRequire(path.join(finalConfig.root, "noop.js")).resolve(finalConfig.typescriptPath);
  ...
  tscBin = path.join(dir, "bin", "tsc");
  runWithNode = existsSync(tscBin);
} catch {}
// otherwise:
spawn("tsc", args, { cwd: finalConfig.root, shell: true })

createRequire only accepts an absolute path or a file URL. With root: '.' the argument is relative, so it throws ERR_INVALID_ARG_VALUE, the empty catch swallows it, and the checker falls back to whichever tsc is on PATH rather than the typescript version the project pins:

"."          -> THROW ERR_INVALID_ARG_VALUE
"<abs path>" -> OK .../node_modules/typescript/lib/version.cjs

Reproduced on a minimal Vite 8 project using the generated Vaadin tsconfig.json: with root: '.' a global TypeScript 5.1.3 was picked up and rejected the generated config with TS6046: Argument for '--target' option must be: ... 'es2022', 'esnext' for "target": "es2023". With root as an absolute path the project-local typescript@7.0.2 is used and the same project reports No errors.

So dev-mode type checking currently depends on the developer's PATH, and environments without a suitable global tsc get either a wrong-version diagnostic or no type checking at all.

The argument-splitting problem this PR addresses could be solved without making the path relative — vite-plugin-checker passes -p and the path as separate array elements, so an absolute root only breaks when the checker joins the arguments into a shell string. Keeping root: __dirname and fixing the quoting upstream, or passing typescriptPath explicitly as an absolute path, would preserve local TypeScript resolution.

[Artur-]

If fi3ework/vite-plugin-checker#792 is merged, we can revert to dirname