Commit a5e232bfe9

ci: analyse each branch as itself, not as main

The scanner ran with no branch name, so every analysis was recorded
against the project's main branch whatever branch produced it — and the
job runs on every push, so a feature branch replaced main's results.

Not theoretical: while dismissing the first scan's false positives the
dashboard was showing an unmerged branch's head, and two findings open on
main read as FIXED on the strength of a commit main does not contain.

Wrong in both directions. A branch that removes findings makes main look
clean before the fix is merged; one that adds findings makes main look
broken when it is not. Once the gate is binding rather than reporting, it
would follow whichever branch built last.

A branch other than main now passes -Dsonar.branch.name and keeps its own
history. main passes nothing and stays the project's default analysis.
The step still ends in `|| true`, so an instance whose plan does not
offer branch analysis loses the branch scans rather than the build — and
main stops being overwritten either way, which is the part that matters.

Closes #154

Layout: unified · split