Changes

• fix(helm): give bundled OpenCost a writable config dir so cost data ships
  • PR: #2878
• fix(cost-agent): make /healthz report a stalled pipeline instead of ok
  • PR: #2880
• fix(ui): stop the side menu sliding under the app header
  • PR: #2881
• test(Common): cover the serialize/deserialize family in JSONFunctions (#402)
  • PR: #2877
• feat(ui): let viewers choose and reorder ModelTable columns
  • PR: #2882
• fix(cost): correct the engine's RAM wire names and dedup ingest per chunk
  • PR: #2883
• feat(cost): collect the peaks and limits right-sizing needs
  • PR: #2884
• fix(metrics): keep the metric explorer time range popup inside the viewport
  • PR: #2886