[Contextual Security] fix group preview opening wrong page index

[alexreal1314]

Summary

This PR addresses the following issue.

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines
• Review the backport guidelines and apply applicable backport:* labels.

Video Recording

Screen.Recording.2025-12-07.at.14.01.21.mov

[elasticmachine]

Pinging @elastic/contextual-security-apps (Team:Cloud Security)

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 7907135

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
securitySolution	11.1MB	11.1MB	+91.0B

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
@kbn/cloud-security-posture-graph	30	31	+1

Total ESLint disabled count

id	before	after	diff
@kbn/cloud-security-posture-graph	32	33	+1

cc @alexreal1314