fix(dgw): reject null event source handles

[Benoît Cortier (CBenoit)]

Treats the null handle returned by RegisterEventSourceW as a registration failure, preventing invalid event source handles from being retained and used for Windows Event Log writes.

Co-authored-by: Copilot App 223556219+Copilot@users.noreply.github.com

[Benoît Cortier (CBenoit)]

Implementation notes:

• Added a focused predicate for the RegisterEventSourceW failure sentinel.
• Preserved the existing Arc ownership, Drop behavior, and immediate registration error path.
• Added a regression proving that NULL, not INVALID_HANDLE_VALUE, denotes failure.

Local validation:

• cargo +nightly fmt --all
• cargo test -p sysevent-winevent
• cargo clippy --workspace --tests -- -D warnings
• cargo test --workspace reached one unrelated, reproducible WindowsApps ACL failure in now-package-broker; 249 tests in that crate passed before the failure.

Note

LLM-assisted content (no human feedback).

[Copilot]

🟢 Approval recommended

The fix and regression coverage are focused, with no unresolved issues.

Pull request overview

Corrects Windows Event Log registration failure detection to match the Win32 API contract.

Changes:

• Rejects null handles returned by RegisterEventSourceW.
• Adds regression coverage for handle sentinel behavior.

File summaries

File	Description
crates/sysevent-winevent/src/lib.rs	Corrects handle validation and adds a focused unit test.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Balanced

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