feat(core): add identity summary directory

[BK1031]

• Add a batched identity-resolution endpoint for user and service-account display metadata
• Return names, usernames, avatars, and owning application visuals without exposing full entity records
• Preserve request ordering, omit unknown identities, and cap requests at 100 IDs

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-31T21:59:02.406036Z	5869cfb	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.