Add net11.0 variant of CI failure scanner

Adds .github/workflows/ci-status-net11.md alongside the main scanner.
Both workflows share the same prompt logic but scan independent branches
with isolated dedup namespaces:

- ci-status-main.md  → scans refs/heads/main, label 'ci-scan'
- ci-status-net11.md → scans refs/heads/net11.0, label 'ci-scan-net11'

Concurrency groups, title prefixes, and labels are namespaced so the two
scanners cannot interfere with each other's issue/PR dedup.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: bot