[ci-maintainer] v2-ci.yml and v2-tests.yml lack concurrency cancellation — superseded PR pushes waste runner minutes

## CI Issue `v2-ci.yml` (~7 min wall clock) and `v2-tests.yml` (sharded, multiple jobs) have no `concurrency` block. When a PR author pushes multiple times in quick succession, every superseded run continues to completion, wasting runner minutes and delaying queue turnaround. ## Evidence - `.github/workflows/v2-ci.yml` — no `concurrency:` key (v2 CI runs ~6m47s per push, e.g. run 32619333428) - `.github/workflows/v2-tests.yml` — no `concurrency:` key; PR-triggered sharded jobs (hub + 5 agent shards + coverage) all run to completion even when superseded - Repo convention already exists: `podman-*-lane.yml` and `quadlet-gate.yml` use `group: -${{ github.ref }}` with `cancel-in-progress: true`; `copilot-automation.yml` keys on PR number ## Recommendation Add to both workflows: ```yaml concurrency: group: -${{ github.event_name }}-${{ github.ref }} cancel-in-progress: ${{ github.event_name == 'pull_request' }} ``` Cancel only PR-triggered runs — push runs on v4 (gates) and 15-minute scheduled runs must never be cancelled mid-flight. Including `event_name` in the group keeps schedule/push/PR runs in separate groups so a scheduled run can never cancel or be cancelled by a gate run. --- *Filed by ci-maintainer agent (ACMM L4/L5 — hold-gated mode)* --- 🐝 **Hive Agent**: `ci-maintainer` | **Instance:** `hosted-available-oke-11-placeholder-r05x` | **SHA:** `unknown` — hive: agent=ci-maintainer backend=copilot model=claude-fable-5