[henrymercer]

The "All-platform bundle" and "CodeQL Bundle All" PR checks are meant to test the all-platform CodeQL bundle. Since #3130, though, prepare-test has returned nightly as the tools URL for nightly-latest regardless of use-all-platform-bundle, so both checks have been testing the platform-specific nightly bundles.

This PR makes prepare-test look up the latest nightly release and return the URL of its all-platform bundle when use-all-platform-bundle is set. It also adds a step to the "All-platform bundle" check that fails unless the bundle contains tools for Linux, macOS and Windows, so that this can't silently regress.

The Ubuntu job of "All-platform bundle" covers everything that "CodeQL Bundle All" tests, so this PR removes "CodeQL Bundle All".

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?

Environments:

• Testing/None - This change does not impact any CodeQL workflows in production.

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?

• Development/testing only - This change cannot cause any failures in production.

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

• Other

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

• Special considerations - CodeQL Bundle All (ubuntu-26.04, nightly-latest) is a required check, so it needs removing from the required checks with pr-checks/sync-checks.ts before this PR can merge.

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]

🟡 Changes recommended

The bundle check uses POSIX dirname on a Windows backslash path, incorrectly checking ./tools and potentially failing Windows PR checks for valid bundles.

1 open issue

• Normalize Windows path separators before resolving the bundle directory · New

What changed in this PR

This PR restores all-platform nightly bundle coverage in the CodeQL Action’s PR checks without changing production behavior.

Changes:

• Resolve an explicit all-platform nightly bundle URL when requested by prepare-test.
• Add a check for Linux, macOS, and Windows tool directories.
• Remove the redundant “CodeQL Bundle All” workflow and its deflake registration.

File	Description
pr-checks/​checks/​all-platform-bundle.yml	Adds validation that the bundle contains tools for all three platforms.
.github/​workflows/​test-codeql-bundle-all.yml	Removes the redundant standalone check.
.github/​workflows/​deflake.yml	Removes the deleted workflow’s retry registration.
.github/​workflows/​__all-platform-bundle.yml	Mirrors the template’s validation step in the generated workflow.
.github/​actions/​prepare-test/​action.yml	Resolves the latest nightly all-platform bundle URL when requested.

_{Review effort: Balanced (auto)}