Fix warning for PAT-like token with username

[mbg]

This was missed in #3563 and caught in #3577 (comment).

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:

• Managed - Impacts users with dynamic workflows (Default Setup, Code Quality, ...).

Products:

• Code Scanning - The changes impact analyses when analysis-kinds: code-scanning.
• Code Quality - The changes impact analyses when analysis-kinds: code-quality.
• Other first-party - The changes impact other first-party analyses.

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?

• 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.

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• Telemetry - I rely on existing telemetry or have made changes to the telemetry.
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  • 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 an incorrect warning emitted by start-proxy when credentials use a PAT-like token with a configured username, and expands unit test coverage to validate the corrected behavior.

Changes:

• Adjust PAT-warning logic in getCredentials to only warn when a PAT is used and no username is provided.
• Refactor/add test utilities (RecordingLogger.hasMessage, assertNotLogged) and expand getCredentials tests to cover username/no-username combinations.
• Add a VS Code snippet file (unrelated to the warning fix).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/start-proxy.ts	Fixes the PAT warning condition to account for username presence for both token and password configs.
src/start-proxy.test.ts	Adds macro-based tests covering PAT warning behavior with/without usernames for token and password inputs.
src/testing-utils.ts	Enhances the recording logger with message-search helpers and adds a negative-log assertion helper.
lib/start-proxy-action.js	Generated output reflecting the src/start-proxy.ts change.
.vscode/tests.code-snippets	Adds an editor snippet (not directly related to the PR’s stated purpose).