Allow .artifacts for changelog CI I/O

[lcawl]

Summary

Unblock changelog submit by allowlisting .artifacts in docs-builder’s changelog CI filesystems.
Also requires elastic/docs-actions#308

Problem

There are a lot of changelog-submit failures since we turned on automatic chagnelog creation in docs-content.
They come from docs-actions passing .artifacts/... paths into docs-builder changelog prepare-artifact, which uses Nullean.ScopedFileSystem and rejects hidden directories.

The failure is in docs-builder: changelog prepare-artifact uses src/Elastic.Documentation.Tooling/FileSystems/RunnerTempFileSystem.cs, which allowlists only .git. Paths under the checkout that start with . are rejected. .artifacts/... is a descendant of the git root, so it is not added as a disjoint CI root.

Solution

HTML/build filesystems already allow .artifacts. Changelog CI should match that for the conventional CI output dir.

Evaluate already uses version: edge, so a docs-builder GHCR edge publish unblocks consumers without a docs-actions tag.

Implementation details

• Allowlisted .artifacts on RunnerTempFileSystem and ChangelogFileSystem
• Added tests/Elastic.Changelog.Tests/Evaluation/ChangelogCiFileSystemTests.cs (allow .artifacts, block .hidden)
• Added PrepareArtifact_ArtifactsPaths_CopiesYamlAndWritesMetadata prepare-artifact regression test

Block assertions now expect ScopedFileSystemException (not UnauthorizedAccessException).

[github-actions]

No actionable issues found. Verdict: approve.

---

What is this? | From workflow: PR Review

Give us feedback! React with 🚀 if perfect, 👍 if helpful, 👎 if not.