XS✔ ◾ Support fork pull request builds

[Muiris Woulfe (muiriswoulfe)]

Purpose

Prevent pull requests from forks from failing when protected credentials are unavailable.

Impact

Fork contributions retain read-only quality checks, while credentialed and write-enabled automation remains limited to trusted branches.

[microsoft-pr-metrics]

PR Metrics

✔ Thanks for keeping your pull request small.
✔ Thanks for adding tests.

	Lines
Product Code	-
Test Code	-
Subtotal	-
Ignored Code	16
Total	16

Metrics computed by PR Metrics. Add it to your Azure DevOps and GitHub PRs!

[Copilot]

Warning

• Copilot's review of this pull request may be incomplete because some of the changed files are excluded by your Copilot content exclusion settings. See Excluding content from Copilot for details.

Pull request overview

Documents CI behavior for fork pull requests while reserving credentialed checks for trusted branches.

Changes:

• Clarifies read-only validation for forks.
• Documents trusted-branch-only checks and maintainer workflow.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
.github/CONTRIBUTING.md	Documents fork and trusted-branch CI behavior.
.github/workflows/build.yml	Excluded by content policy; not reviewed.

Files excluded by content exclusion policy (1)

• .github/workflows/build.yml

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