ci: pin third-party GitHub Actions to verified release SHAs

[Vamshi-Microsoft]

Purpose

• Replace the tj-actions/changed-files action in broken-links-checker.yml with a built-in git diff step that detects changed Markdown files between the PR base and head SHAs, preserving the any_changed / all_changed_files outputs consumed by the lychee step. This removes a third-party dependency from change detection.
• Pin third-party GitHub Actions to specific release commit SHAs (instead of mutable version tags) for reproducible and immutable workflow runs.

Does this introduce a breaking change?

• Yes
• No

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid
Changed files:

• .github/workflows/broken-links-checker.yml
• .github/workflows/pr-title-checker.yml
• .github/workflows/test.yml

Other Information

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
TOTAL	3055	381	87%

report-only-changed-files is enabled. No files were changed during this commit :)

Tests	Skipped	Failures	Errors	Time
886	5 💤	0 ❌	0 🔥	8.339s ⏱️

[Copilot]

Pull request overview

This PR hardens CI workflows by making third-party GitHub Action references immutable (pinned to specific commit SHAs) and removes a third-party dependency for detecting changed Markdown files in the broken-links workflow.

Changes:

• Replaced tj-actions/changed-files with a git diff-based step that preserves any_changed / all_changed_files outputs for downstream lychee usage.
• Pinned lycheeverse/lychee-action, amannn/action-semantic-pull-request, and MishaKav/pytest-coverage-comment to specific release commit SHAs.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/broken-links-checker.yml	Replaces third-party changed-files action with git diff output wiring and pins lychee action to a SHA.
.github/workflows/pr-title-checker.yml	Pins the semantic PR title checker action to a specific release SHA.
.github/workflows/test.yml	Pins the pytest coverage comment action to a specific release SHA.

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[Vamshi-Microsoft]

Addressed the Copilot review comment: removed the leftover "with:/files:" block that remained after converting the tj-actions/changed-files step to a built-in git diff run: step. "with:" is only valid for "uses:" action steps, so leaving it would have made the workflow YAML invalid. The file now passes YAML validation.