refactor(metrics): Isolate visible sampling sessions

[bigtomcat6]

Summary

Refactor energy impact data flow so sampling is isolated to currently visible sessions:

• Split sampling-session filtering into EnergyImpactSampler and move related orchestration out of the provider and model.
• Update EnergyImpactProvider and EnergyImpactModel to consume the isolated sampler output.
• Expand unit test coverage across app and core energy-impact paths to preserve behavior during the refactor.

How to test

• Run the affected energy-impact focused test suites before/after the refactor.
• Manually verify the Energy Impact screen with a representative sampling workload and confirm visible-session totals align with expectations.

Release impact

• Type: Fixed
• Release note:
  • Restrict energy-impact sampling calculations to visible sessions so metrics are no longer affected by invisible/filtered sessions.

Checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title follows type(scope): Summary.
• Tests or a clear manual verification path are included.
• User-facing changes include release-note wording or Release impact: None.

[codecov]

Codecov Report

❌ Patch coverage is 90.41488% with 67 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...tyCore/Metrics/Providers/EnergyImpactSampler.swift	91.25%	48 Missing ⚠️
...yCore/Metrics/Providers/EnergyImpactProvider.swift	67.85%	18 Missing ⚠️
...rces/MacActivityApp/Models/EnergyImpactModel.swift	98.93%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[bigtomcat6]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Already looking forward to the next diff.

Reviewed commit: c40087a1c4

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[bigtomcat6]

reviewed