Add Windows C++ MSBuild and PowerShell diagnostics

[isink17]

Summary

Adds a Windows legacy C++ diagnostics layer on top of the existing C++/MSBuild/PowerShell handler branch.

Implemented:

• MSBuild/VC++ first-error summary with project failure grouping
• MSB3073/MSB3721 command and exit-code extraction
• broader VC++/linker/resource compiler error detection
• safer PowerShell Select-String rewrites
• compact Get-ChildItem subset via rtk gci
• rtk read --lines A:B
• UTF-16 no-BOM detection and safer binary-ish file preview
• rtk log --events N for recent deduped error/assert/load events

Validation

Local validation passed:

• cargo fmt --all -- --check
• cargo clippy --all-targets
• cargo test --all
• cargo build --release
• .\target\release\rtk.exe --version
• .\target\release\rtk.exe gain

Notes

rtk gci intentionally supports a safe subset of PowerShell Get-ChildItem semantics. Complex variable/pipeline/quoted-path cases should avoid unsafe rewrites and fall back instead.

[gemini-code-assist]

Code Review

This pull request introduces several enhancements, including a new PowerShell-compatible gci command, improved MSBuild diagnostic parsing with context extraction, recent event tailing in log analysis, and robust UTF-16 auto-detection. The review feedback highlights critical compilation errors caused by using the non-standard is_multiple_of method on usize. Additionally, there are valuable recommendations to optimize performance by avoiding heap allocations during byte sampling and using a HashSet instead of a Vec for O(N) deduplication. Finally, the feedback addresses correctness issues regarding case-insensitivity in glob matching and handling quoted paths with spaces during command rewriting.