fix(ci): upgrade eslint to v10 by removing incompatible eslint-plugin-github

[Copilot]

eslint-plugin-github@6.0.0 declares eslint@^8 || ^9 as a peer dependency, blocking npm ci entirely after the eslint v10 bump.

Changes

• Remove eslint-plugin-github — all its rules (github/*, eslint-comments/*, filenames/*, import/*, i18n-text/*) were already explicitly disabled in the flat config, making the dependency a no-op
• Add @eslint/js as an explicit devDependency — required for eslint v10 flat config (js.configs.recommended)
• Clean up eslint.config.js — remove the plugin import, its registration in plugins, and all now-orphaned rule overrides
• Fix no-useless-assignment in global-announce.ts — new rule enforced by eslint v10; resolved by merging the redundant initializer into the first real assignment:

  // before
  let liveRegion: LiveRegionElement | null = null
  liveRegion = from ? getClosestLiveRegion(from) : null
  
  // after
  let liveRegion: LiveRegionElement | null = from ? getClosestLiveRegion(from) : null

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[changeset-bot]

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Latest commit: 0ab800f

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