fix: automatically switch to fetch mode when runtime is set

[ClarkXia]

This pull request introduces a new feature to automatically switch to "fetch" mode when the runtime option is set, along with related updates to improve functionality and documentation. The changes primarily focus on enhancing the handling of the runtime option in script loading and updating relevant files to reflect the new version.

[Copilot]

Pull Request Overview

This PR introduces a feature to automatically switch to "fetch" mode when the runtime option is set and updates the related configuration logic and documentation.

• Update the configuration merge in apps.ts to consider the runtime option.
• Refine runtime-related log messages in AppRoute.tsx.
• Update version and changelog for the new release.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
packages/icestark/src/apps.ts	Includes runtime in deconstruction and condition update
packages/icestark/src/AppRoute.tsx	Refactors runtime handling with error and warning logs
packages/icestark/package.json	Bump version from 2.8.3 to 2.8.4
CHANGELOG.md	Updates changelog with the new fix entry

Comments suppressed due to low confidence (1)

packages/icestark/src/apps.ts:384

• The condition (runtime && runtime.length > 0) assumes that runtime is always an array or a string. Please ensure that runtime's type is consistent throughout the codebase or add the appropriate type-checking to improve code clarity.

const loadScriptMode = appConfig.loadScriptMode ?? (umd || sandboxEnabled || (runtime && runtime.length > 0) ? 'fetch' : 'script');