Fix CI: upgrade ESLint to 10 compatibility

[Copilot]

eslint-plugin-github@6.0.0 only supports eslint@^8 || ^9, blocking the ESLint 10 upgrade. The flat config wasn't actively using any rules from that plugin (all were turned off), making removal safe.

Changes

• package.json: Remove eslint-plugin-github; add missing @eslint/js (required by flat config)
• eslint.config.js: Remove eslint-plugin-github import and its unused rule overrides (github/no-inner-html, i18n-text/no-en)
• global-announce.ts: Fix no-useless-assignment error introduced by ESLint 10's new rule — replaced let + redundant null init with const declarations

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 7d7977d

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[liuliu-dev]

@copilot resolve conflicts

[Copilot]

@copilot resolve conflicts

Resolved in commit 3e1f08f. The base branch had accumulated additional dependency bumps (@changesets/cli → ^2.30.0, publint → ^0.3.18, a11y-dialog → ^8.1.5) that weren't reflected in our branch. Updated all three package.json files and regenerated package-lock.json.

[liuliu-dev]

@copilot resolve conflicts

[Copilot]

@copilot resolve conflicts

Resolved in commit 360f99f. The package-lock.json had diverged because both branches made substantial changes to it — regenerated it by starting from the base branch's lock file then re-running npm install with our package.json (which removes eslint-plugin-github and adds @eslint/js). This produces a lock file that is forward-based on the base branch, clearing the merge conflict.