Support skipping workflow validation

[mbg]

For internal use, we have CodeQL workflows that we know are valid and don't require validation on every run. This PR changes workflow validation so that it is always skipped for dynamic workflows. It also adds an environment variable which allows us to skip workflow validation.

This PR also slightly refactors the check into a function in workflow.ts and adds test coverage.

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?

• Advanced setup - Impacts users who have custom workflows.
• Default setup - Impacts users who use default setup.
• Code Scanning - Impacts Code Scanning (i.e. analysis-kinds: code-scanning).
• Code Quality - Impacts Code Quality (i.e. analysis-kinds: code-quality).
• GHES - Impacts GitHub Enterprise Server.

How did/will you validate this change?

• Unit tests - I am depending on unit test coverage (i.e. tests in .test.ts files).
• 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.
  • Dashboards - I will watch relevant dashboards for issues after the release. Consider whether this requires this change to be released at a particular time rather than as part of a regular release.
  • Alerts - New or existing monitors will trip if something goes wrong with this change.

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 introduces an environment variable to skip workflow validation for internal use cases where workflows are known to be valid. The main changes include:

1. Refactored workflow validation check into a dedicated checkWorkflow function in init.ts
2. Added SKIP_WORKFLOW_VALIDATION environment variable to control validation
3. Added comprehensive test coverage for the new function

Reviewed Changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/init.ts	Added checkWorkflow function wrapping validation logic with environment variable check
src/init-action.ts	Replaced inline workflow validation with call to new checkWorkflow function
src/environment.ts	Added SKIP_WORKFLOW_VALIDATION enum entry with documentation
src/init.test.ts	Added three test cases covering validation, error logging, and skip scenarios
lib/*.js	Generated JavaScript code from TypeScript sources (auto-generated)