chore(build): enable Rspack runtime mode

[Timeless0911]

Motivation

Enable Rspack's experimental runtime output for the three packages published from this repository. This reduces the internal runtime overhead and aligns the ESM bundle output with Rspack's named runtime bindings.

Changes

Configure tools.rspack.experiments.runtimeMode as "rspack" for @rslib/core, rsbuild-plugin-dts, and create-rslib. The generated runtime now uses named ESM exports such as rspackRequire and moduleFactories; create-rslib has no standalone runtime chunk and is unchanged.

Validation:

• Built all three packages successfully.
• Package tests passed: core 116, plugin-dts 30, create-rslib 39.
• pnpm lint passed.
• Generated JavaScript passed node --check and public ESM import smoke tests.
• gzip size changed by -18 B for core and -52 B for plugin-dts; create-rslib was unchanged.

The option remains experimental in Rspack, so future Rspack minor releases may change its runtime output.

[Copilot]

🟢 Approval recommended

All reviewed changes have been assessed with no unresolved blocking issues.

Pull request overview

Enables Rspack runtime mode for the three published packages.

Changes:

• Configures runtimeMode: 'rspack' for core, plugin-dts, and create-rslib.
• Preserves existing package-specific settings.

File summaries

File	Description
packages/plugin-dts/rslib.config.ts	Enables Rspack runtime mode.
packages/create-rslib/rslib.config.ts	Enables Rspack runtime mode.
packages/core/rslib.config.ts	Enables Rspack runtime mode.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 0
• Review effort level: Lite

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