Node disk history: surface the pool-mirror footprint

Found during Task 7530's visual check of the node page's Health → Disk history. Suggestions: 1. A reclaim that freed nothing collapses into the quiet "no-op" run (`isNoop` in apps/web/src/components/NodeDiskEvents.tsx), so its `remaining_bytes` (Git mirrors, Plugin folder) can't be seen on a quiet node. Count a reported remaining size as something to show, or show the latest one in the Disk panel header. 2. At 1280px the floating Help/assistant button sits over the Disk panel's bottom-right corner, covering part of a row. Reserve space for it, or move it clear of panel content. 3. The Disk panel is narrow on desktop, so engine names in monospace wrap first. Let the panel use the column width. Out of scope: the reclaim pass and the report payload (Task 7530). Done means: - On a node whose latest reclaims freed nothing, the Git mirrors size is visible without expanding a collapsed run. - At 1280px and 448px the Help button covers no Disk-history text (screenshots).

Disk header now shows the newest Git mirrors/Plugin folder sizes; mono engine names wrap whole. Visual check at 1280/448: launcher covers no text. Full gate timed out (load ~105, no failing test); PR #6085 is queued on the merge lane. Draft follow-up #7574.