[QoL/enhancement] enable direct feedback for PR comment triggers like `uptest`

From Erhan:

> re: uptest trigger, nit idea for the future, if we are interested & have capacity.
> today, uptest trigger comments have no direct "feedback" about the trigger itself. For example, with new changes, after you comment, you need to go and check the actions UI, find your PR. You see a green job, but the trigger step is just skipped.
> For the happy path, you still need to monitor and wait for the triggered uptest job itself.
>
> Another dream: :sweat_smile: Sometimes we trigger multiple uptest runs. It can get messy to find out which ones passed and the associated job links. Also, sometimes they disappear from the "Succeeded checks" section in the PR overview page (possibly when results are expired?). Then we don't know whether the last run succeeded, especially for PRs that were parked for a while etc.
> Maybe we can append the triggered job URL (and maybe the job result) somehow to the associated comment. might make it a bit easier to track uptest runs.

This feels like a reasonable improvement so that users don't have to babysit pipeline runs.

Start by locating the workflow entry point that handles `uptest` PR-comment triggers and trace how it launches the GitHub Actions job. Define how the associated comment should expose the triggered job URL and result, including multiple runs; done should make each trigger and its outcome discoverable without searching the Actions UI.

Written by the indexing model from the issue text.