Count failed jobs of the shown tag only on the service line

[lesnik512]

The service line counted every failed job between production and the head: every row's main pipeline and every tag pipeline, including untagged rows above the newest tag. A failure fixed a few merges later, or one in a commit no tag ships yet, kept the count red even when the tag about to be released was green.

The line now counts only the jobs of the tag it is about:

• the picked tag, or the newest tag before any pick, prefixed with its name (1.2.0: ❌ 1 failed) since the line does not show that tag otherwise;
• that tag's own pipeline and the main pipeline of its commit, because many setups run tests only on main and only deploy jobs on tags;
• no count without a tag; the untagged badge covers that case.

Allowed-to-fail jobs are still counted separately. The failed-jobs column of the opened service is unchanged, so the failures of other rows stay one click away. Page only: the report and its schema are unchanged.

The page's JavaScript has no tests, so I checked it in a browser against a sample report with failures in three rows. Before a pick the line read 1.2.0: ❌ 1 failed · 1 failed, allowed to fail, and after picking 1.1.0 it read ❌ 2 failed. The old code showed 4 failed and 1 allowed in both cases.