Fix broken log grouping due to nested log group

[henrymercer]

The "Computing PR diff ranges" log group was nested within the "Load language configuration" log group. Since Actions doesn't support nested log groups this was creating some noise in the logs where the last part of "Load language configuration" spilled out into the top-level logs.

This PR simply removes the "Computing PR diff ranges" log group in favour of a log message instead.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

Workflow types:

• Advanced setup - Impacts users who have custom CodeQL workflows.
• Managed - Impacts users with dynamic workflows (Default Setup, Code Quality, ...).

Products:

• Code Scanning - The changes impact analyses when analysis-kinds: code-scanning.

Environments:

• Dotcom - Impacts CodeQL workflows on github.com and/or GitHub Enterprise Cloud with Data Residency.
• GHES - Impacts CodeQL workflows on GitHub Enterprise Server.

How did/will you validate this change?

• End-to-end tests - I am depending on PR checks (i.e. tests in pr-checks).

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

• Rollback - Change can only be disabled by rolling back the release or releasing a new version with a fix.

How will you know if something goes wrong after this change is released?

• Telemetry - I rely on existing telemetry or have made changes to the telemetry.
  • Alerts - New or existing monitors will trip if something goes wrong with this change.

Are there any special considerations for merging or releasing this change?

• No special considerations - This change can be merged at any time.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[Copilot]

Pull request overview

This PR fixes noisy/mis-grouped GitHub Actions logs by removing a nested log group (“Computing PR diff ranges”) that was being emitted while already inside the “Load language configuration” group (nested log groups aren’t supported). The diff-range computation is now indicated via a plain informational log message instead of a group.

Changes:

• Remove the withGroupAsync("Computing PR diff ranges", ...) wrapper from prepareDiffInformedAnalysis.
• Add a logger.info("Computing PR diff ranges...") message at the start of computeAndPersistDiffRanges.

Show a summary per file

File	Description
src/diff-informed-analysis-utils.ts	Removes the nested log group and replaces it with a simple info log to avoid broken grouping output.
lib/entry-points.js	Generated build output reflecting the TypeScript change (not reviewed).

Copilot's findings

• Files reviewed: 1/2 changed files
• Comments generated: 0