Fix live main limit capacity pooling

[cbusillo]

Summary

• exclude failed/stale/expired buckets from live main-limit capacity math
• exclude shorter-window buckets when the same account is blocked by an exhausted longer main window
• use live buckets for burn-rate estimates and preserve observed burn-rate copy in OpenAI guardrail forecasts
• document the live-capacity rule

Verification

• swift test --filter 'mainLimitSummaries|observedBurnRate|capacityPortfolioDetailKeepsBurnRate|openAIFastModeForecastHelper'
• scripts/commit-gate.sh
• scripts/context-panel-runtime-baseline.sh install --launch
• scripts/context-panel-runtime-baseline.sh check

Notes

• JetBrains changed-file inspection only reported spelling warnings for the canonical bundle identifier com.shinycomputers.contextpanel.