Cap Vitest worker concurrency to keep the suite deterministic

Vitest 4 defaults its worker count to roughly the host CPU count. On
high-core machines that are also running other work (e.g. several dev
stacks), that oversubscribes the cores and starves test event loops,
making timing-sensitive component tests (mount-then-query) flake
intermittently. Vitest 2 did not exhibit this under the same suite.

Cap maxWorkers so the run stays deterministic. CI runs on far fewer
cores than this binds, so it is not slowed there; the cap only takes
effect on big multi-core machines where the default oversubscribes.

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

Author: alistair3149

resources/ext.neowiki/vitest.config.ts

@@ -5,6 +5,13 @@ export default mergeConfig( viteConfig, defineConfig( {
 	test: {
 		environment: 'jsdom',
 		globals: true,
+		// Cap worker concurrency. Vitest's default (~CPU count) oversubscribes
+		// high-core machines that are also running other work, starving test
+		// event loops and making timing-sensitive component tests flake. A fixed
+		// cap keeps the suite deterministic without slowing CI, which runs on far
+		// fewer cores than this binds.
+		maxWorkers: 4,
+		minWorkers: 1,
 		coverage: {
 			provider: 'v8',
 			include: [ 'src' ],