perf: disable Rspack config schema validation

[chenjiahan]

Summary

Disable Rspack's config schema validation to improve performance.

Rsbuild has ensured that the built-in Rspack configuration is correct through TypeScript, so it is usually redundant to perform schema validation at runtime. Disabling schema validation can improve performance by 20ms to 30ms.

This can be manually enabled via RSPACK_CONFIG_VALIDATE=strict:

RSPACK_CONFIG_VALIDATE=strict rsbuild build

Related Links

See web-infra-dev/rspack#10768 for performance comparison.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR disables Rspack's config schema validation by default to improve performance, while still allowing manual strict validation via an environment variable override.

• In packages/core/src/plugins/basic.ts the default validation is changed to 'loose-silent' to disable runtime schema checks.
• In e2e/playwright.config.ts strict validation is forced for test environments.
• In e2e/cases/config/rspack-config-validate/index.test.ts tests are updated to temporarily set the validation mode for warning scenarios.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/core/src/plugins/basic.ts	Default config validation is disabled for performance gains.
e2e/playwright.config.ts	Test environment explicitly enables strict config validation.
e2e/cases/config/rspack-config-validate/index.test.ts	Tests adjusted to temporarily override validation mode.

Comments suppressed due to low confidence (2)

packages/core/src/plugins/basic.ts:98

• [nitpick] The comment accurately explains the new default behavior, but consider adding a brief note that this behavior can be overridden in test environments to clarify the rationale for differing modes between production and testing.

        process.env.RSPACK_CONFIG_VALIDATE ||= 'loose-silent';

e2e/cases/config/rspack-config-validate/index.test.ts:26

• [nitpick] The test temporarily sets RSPACK_CONFIG_VALIDATE to 'loose-unrecognized-keys' even though the production default has shifted to 'loose-silent'; consider adding a clarifying comment to explain why this override is necessary for the warning test scenario.

  const value = process.env.RSPACK_CONFIG_VALIDATE;