reactions-avatars - Fix on React issues - #10264

Created by Claude, will be reviewed by @fregante first.

The React issue view only lists the full names of the reactors, not their usernames. The reactors of all comments in view are now fetched in a single batched GraphQL request (comments by node ID, the description by issue number), using the avatar URLs from the API. This path needs a token, without one no avatars are shown there.

Fixes #10048

Test URLs:

• PR: Help users find a feature with an interactive binary search #4119
• Locked PR: Add "Wait for successful checks" checkbox #975
• Copilot reaction: Expose old feature names in more places #7761
• Dependabot reaction: Bump cython from 0.29.9 to 0.29.10 aio-libs/aiohttp#3809 (comment)
• Discussion: Build error when using JS imports: Browser scripts cannot have imports or exports parcel-bundler/parcel#6490
• Locked discussion: https://github.com/orgs/community/discussions/28776
• Deferred participants loading: https://github.com/orgs/community/discussions/30093
• Releases: https://github.com/refined-github/refined-github/releases
• React issue: extend-repo-tabs: Preserve the native “Pull requests” label #10026