Main2Dev @W-22462053@ Merging main to dev after v5.16.0

[svc-cli-bot]

This branch and PR were automatically created following the successful release of v5.16.0.
It must be MERGED into dev, NOT SQUASHED OR REBASED. Squashing or rebasing this branch onto dev can cause potentially irreconcilable merge conflicts later.
As an additional safeguard and reminder, the title of this PR MUST include the word 'merging' in the description portion of the PR title, e.g., 'Main2Dev @W-XXXXXXX@ Merging main to dev after vX.Y.Z'.
If there are conflicts between dev and this branch, you should do the following locally:

• $ git checkout dev
• $ git pull
• $ git fetch --all
• $ git checkout m2d/v5.16.0
• $ git pull origin dev --no-rebase # You MUST include this flag, or someone's day will be ruined.
• Resolve the merge conflicts manually. When in doubt, ask the code's author for help.
• $ git commit
• $ git push

[aruntyagiTutu]

Content reviewed and looks correct:

• Version bump to 5.16.0 in package.json/package-lock.json matches the just-released v5.16.0.
• validate-pr.yml change extends the existing PR-title-injection fix (from #2079/@W-19079373) to also pass head_ref via the environment instead of direct ${{ startsWith(github.head_ref, ...) }} interpolation in the bash conditional — same injection-hardening pattern, good consistency.

One actionable item before merge: the PR's own body instructs renaming the title to include 'merging' (e.g. 'Main2Dev @W-XXXXXXXX@ Merging main to dev after v5.16.0'), and the 'Verify that PR title contains well-formed GUS work item tag' check is currently failing because the placeholder title ('Filler title. Read description and rename.') hasn't been updated yet. No code concerns — just needs the rename to go green and merge, consistent with prior Main2Dev PRs (#2072, #2058).

[aruntyagiTutu]

Title has been renamed to the correct Main2Dev format and the PR-title-validation check now passes. Content unchanged from my prior review — version bump to 5.16.0 and the head_ref/base_ref injection-hardening fix are correct. CI green. Approving.