perf(server): fix N+1 PowerShell process query and reduce sampling frequency

[UtkarshUsername]

What Changed

Eliminated two sources of excessive CPU usage in the Windows process resource monitor:

1. N+1 PowerShell CIM query to bulk query (ProcessDiagnostics.ts): The Windows process reader was querying Win32_PerfFormattedData_PerfProc_Process individually for each process via an IDProcess filter inside a ForEach-Object loop. Changed to query all perf counter data once into a hashtable, then join with the process list. Reduced from 1+N CIM queries to exactly 2.
2. Sampling interval 5s to 15s (ProcessResourceMonitor.ts): Tripled the interval between resource samples, reducing overhead 3x while maintaining adequate granularity for multi-second bucket aggregation.

Why

On Windows machines with 200+ processes, ProcessResourceMonitor was spawning powershell.exe every 5 seconds with an N+1 WMI query pattern. Each cycle issued 1+N CIM queries (e.g., 206 queries for 205 processes). The old command consistently timed out after 60 seconds on a typical development machine, pegging CPU indefinitely.

Metric	Before	After	Improvement
Per-query time	>60s (timed out)	~2.7s	≥22x+
CIM queries per cycle	1+N (e.g., 206)	2	~100x
Sampling interval	5s	15s	3x
Effective overhead	100% CPU (never finishes)	~18% for 2.7s	≥66x

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

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Note

Low Risk
Diagnostics-only changes on Windows sampling path; behavior is coarser metrics (15s) but lower server CPU load, with no auth or data-path impact.

Overview
Reduces Windows process diagnostics overhead by fixing how PowerShell loads CPU perf data and by sampling less often.

Windows process query: readWindowsProcessRows no longer runs a filtered Win32_PerfFormattedData_PerfProc_Process CIM call inside the per-process loop. It loads all perf rows once into a hashtable keyed by IDProcess, then walks Win32_Process and joins in memory—two CIM queries per cycle instead of 1+N.

Resource monitor: SAMPLE_INTERVAL_MS moves from 5s to 15s, so the background sampler runs three times less often. Approximate CPU-second rollups use the new interval; tests now expect 6 instead of 2 for the same two-sample scenario.

^{Reviewed by Cursor Bugbot for commit 9d9363e. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix N+1 PowerShell process query and increase sampling interval to 15s

• Rewrites readWindowsProcessRows in ProcessDiagnostics.ts to preload all Win32_PerfFormattedData_PerfProc_Process entries into a hashtable keyed by IDProcess, eliminating a per-process WMI query.
• Increases SAMPLE_INTERVAL_MS in ProcessResourceMonitor.ts from 5,000 ms to 15,000 ms to reduce polling overhead.
• Behavioral Change: process CPU metrics are now refreshed every 15s instead of every 5s.

^{Macroscope summarized 9d9363e.}

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[macroscopeapp]

Approvability

Verdict: Approved 2db1250

Performance optimization fixing N+1 PowerShell process query and reducing diagnostic sampling frequency from 5s to 15s. Self-contained changes to monitoring code with corresponding test updates.

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