Move S3 credential guidance into a field tooltip

[klboke]

Summary

Move the S3 credential explanation from always-visible text below the selector into the existing help icon beside the Credentials label. The guidance appears on hover or keyboard focus, matching other admin forms.

Escape dismisses the open tooltip while preserving the form and unsaved input. A second Escape retains normal modal dismissal. Update the admin script version so browsers fetch the corrected shared tooltip handler.

Related to #301. Follow-up to #302.

Validation

• mvn -pl admin-ui -am test — 38 tests passed.
• node --test admin-ui/src/test/js/blobstore-credentials.test.js — 6 tests passed. The new Escape regression test failed before the fix.
• mvn -pl server -am compile -q.
• git diff --check.
• Verified on the local dev instance at port 18090: help is hidden initially and appears on hover or keyboard focus. First Escape hides the tooltip and preserves the open form and unsaved name; second Escape closes the form.
• Server/compatibility test suites and Full E2E, live compatibility, real client, and Native E2E workflows are not applicable to this client-side tooltip change.

Compatibility and design checklist

• No protocol behavior changes.
• No protocol compatibility test changes needed; the keyboard regression is covered in the existing admin JavaScript suite.
• No state, cache, locking, session, background task, upload/delete, metadata, or permission changes.
• No migration changes.

Notes for reviewers

Uses the existing field-label, field-help, and icon-info markup. The explanation text is unchanged. The shared tooltip handler consumes Escape only while its popover is visible.

[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 2026-09-18T15:12:03.503721Z	ffb3310	New commits

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.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 25012772bd

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".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.17%. Comparing base (cd2f17d) to head (ffb3310).

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #304   +/-   ##
=========================================
  Coverage     86.17%   86.17%           
  Complexity     1447     1447           
=========================================
  Files           794      794           
  Lines         83247    83247           
  Branches      14612    14612           
=========================================
+ Hits          71737    71738    +1     
+ Misses        11510    11509    -1     

Flag	Coverage Δ
server-smoke-mysql	13.26% <ø> (-0.02%)	⬇️
server-smoke-postgresql	13.28% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.