Fix backslashes being accepted by sanitizeArtifactName

[mbg]

Artifact names may not contain backslashes, but sanitizeArtifactName accepts them, potentially resulting in errors during debug artifact uploads:

Warning: Failed to upload debug artifacts: Error: The artifact name is not valid: foo\\bar Contains the following character:  Backslash \

This PR removes them from the list of acceptable characters in the regex and adds a test case.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Confirm the readme has been updated if necessary.
• Confirm the changelog has been updated if necessary.

[Copilot]

Pull Request Overview

This PR tightens the sanitizeArtifactName regex to disallow backslashes and adds a corresponding test case to prevent debug upload errors.

• Removed backslash (\) from allowed characters in the regex for artifact names.
• Added a test case to verify backslashes are stripped out.
• Updated both TypeScript sources and compiled JavaScript outputs to keep them in sync.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

File	Description
src/debug-artifacts.ts	Updated regex to disallow backslashes in names.
src/debug-artifacts.test.ts	Added test case for backslashes in names.
lib/debug-artifacts.js	Mirrored regex update in compiled output.
lib/debug-artifacts.test.js	Mirrored test addition in compiled tests.

Comments suppressed due to low confidence (1)

src/debug-artifacts.test.ts:21

• Consider adding a test case to ensure valid characters like hyphens and underscores are preserved (e.g., foo-bar_baz → foo-bar_baz).

t.deepEqual(