fix: replace deprecated wmic process stats with CIM query

[peschuster]

Problem

ChildProcessTracker polls per-process CPU/memory stats on Windows via
execFileSync('wmic', ...). wmic has been deprecated for years and is
removed from current Windows 11 builds (24H2+), so usage polling silently
fails on up-to-date systems.

There are two additional issues in the same code path:

• The memory value is overstated 1024x: WorkingSetSize is reported in
  bytes, but the code multiplies by 1024 as if it were KB. The 100 MB
  warning threshold therefore effectively fired at ~100 KB for every
  tracked process.
• The two execFileSync calls block the event loop on every 10-second
  polling tick, and their column-based text output is locale-sensitive.

Solution

Replace the two blocking wmic calls with a single async PowerShell
Get-CimInstance query. Win32_PerfFormattedData_PerfProc_Process
provides both PercentProcessorTime and WorkingSet in one call, and
ConvertTo-Json makes the output locale-independent and robustly
parseable. Parsing lives in an exported parseCimProcessStats helper with
unit tests (single object, array result, empty output for an
already-exited process, missing properties, malformed output).

Testing

processUtils.test.ts on Windows 11 (German locale): 13 passing with this
change. Note: one pre-existing "after each" hook failure in the
ChildProcess suite (mock-fs/rimraf cleanup on Windows) occurs identically
with and without this change on current main.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.