[Pranav-IIITM]

Closes #1000

What changed

• The Check links step in CI now gets the same GitHub token that the Test and Build steps already use.
• If the latest pack version can't be looked up, the build now says so clearly and suggests how to fix it, instead of failing with a confusing jq parse error.

Why

Check links was looking up the latest pack version without a token. On GitHub's shared runners that request can hit the anonymous rate limit, which made the build job fail at random on PRs that had nothing wrong with them. Contributors can't re-run the job themselves, so they had to push empty commits just to get a fresh run.

With this change, CI should stop failing for reasons unrelated to the PR, and if the lookup does fail, the error says what went wrong.

[Pranav-IIITM]

Evidence of the flaky failure, from CI runs on #999, which doesn't touch CI or the Makefile:

Run	Commit	Version lookup in Check links	Result
Run 1	ee28c4c4	❌ jq: parse error: Invalid numeric literal → make: *** [Makefile:111: pack-version] Error 1	failed
Run 2	8a876dd7 (empty commit, same code as run 1)	✅ PACK_VERSION=0.40.10	lookup worked; the job later failed on an unrelated broken link that was fixed in #999
Run 3	365d4ef2	✅ PACK_VERSION=0.40.10	passed

Runs 1 and 2 used identical code and the same workflow, yet the version lookup failed in one and worked in the other. That fits the anonymous GitHub API rate limit on shared runners: Check links makes the request without GITHUB_TOKEN, so whether it works depends on how much of the runner IP's anonymous allowance is left.