Optimize PowerShell script and restructure README

[marcelloformica]

Summary

Performance optimizations for the PowerShell script and a full README restructure to eliminate redundancies.

PowerShell script changes

Performance

• Compiled MetricProcessor via Add-Type (C#): the ~44K-datapoint-per-resource JSON processing loop runs at native .NET speed instead of interpreted PowerShell
• Compiled GapProcessor via Add-Type (C#): ExpandToTickSet and ClassifyGaps replace interpreted loops for gap investigation
• Shared HttpClient with connection pooling for per-resource metrics and gap investigation (replaces per-call Invoke-WebRequest TCP/TLS overhead)
• HashSet-based O(1) interval containment for suspect-minute classification
• TryGetProperty hash lookup instead of EnumerateObject linear scan

Bug fixes

• Per-resource ARM metric URL now includes metricnamespace parameter (fixes SQL databases showing 0 0 N/A)
• Case-insensitive metric name comparisons in compiled C# (matching PowerShell -eq behavior)
• Idempotent Add-Type guards: two independently guarded blocks so the script can be re-run within the same PowerShell session

Code quality

• Added/improved comments on complex code blocks (classification logic, interval merging, gap counting, result assembly)
• Updated section headers for consistency

README changes

Restructured from 7 scattered sections into 3 clean sections:

1. Introduction — what it does, two implementations, key questions
2. Usage — prerequisites, parameters, examples, output
3. How it works — inventory, metrics, gap investigation, result assembly, worked example, implementation notes

Removed redundancies:

• Suspect = Faults + Excused + Unresolved invariant (was stated 3 times)
• Health History retention (mentioned 4+ times)
• 90-day lookback constraint (intro, parameters, architecture notes)
• Storage zero-tx handling (Step 2, Step 4, separate subsection, architecture notes)
• Customer-initiated detection fields, conservative-on-failure, batch API details, Native AOT, pipeline output (each duplicated)