Fix Windows process fixtures and use Apache-licensed assertions

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Windows native-package validation failed after the bounded process runner correctly timed out: Windows PowerShell could be terminated during cold startup before publishing the PID file, and the fixture then tried to read that missing file. The existing native crash probe now publishes its live PID atomically and holds without output. The timeout test validates readiness before awaiting timeout, while preserving its three-second deadline, seven-second bound, cancellation-token checks and live process-tree termination proof. The production process runner is unchanged.

Replace FluentAssertions 8.11.0 in the three test projects with AwesomeAssertions 9.6.0, whose NuGet package and exact source license declare Apache-2.0. The resolved net10 dependency group adds no packages or paid activation mechanism. Test references are private, and the namespace migration preserves existing assertion calls. Development documentation records the licensing choice and update policy.

Validation:

• Authenticated failing main run 37199672539: Windows 20 passed / 1 failed / zero skips. The failure occurred after timeout and elapsed-bound assertions passed.
• Local Debug solution build passed; process-runner cases passed 7/7 with zero skips. Silent timeout completed in 3.066 seconds and tree timeout in 3.138 seconds.
• All 21 restored project dependency graphs contain no FluentAssertions. AwesomeAssertions is confined to the three test projects.
• Full local generic Debug suite passed 2,534/2,534 (20 integration, 2,227 unit/runtime, 246 component, 41 Playwright), with strict successful receipts and zero skips. Final-head hosted PR CI run 37202079928 passed all 21 checks. Authenticated artifact receipts confirm 2,534/2,534 generic tests, 21/21 Windows tests, 3/3 macOS tests and 1/1 native gateway test, with zero failures or skips. The formerly failing Windows case passed in 3.025 seconds; Windows and .NET logs contain no Xceed or Fluent Assertions warnings.

Product version remains 0.1.0. Existing CI jobs, timeouts, assertions and receipt requirements are preserved. Merged as af6a7ed84de4463097258f44199cbd1c6fbbc3c9 after all 21 checks passed. The resulting main-push CI run 37203248412 passed all 21 checks, with no failed or skipped jobs. Its Windows suite passed 21/21, including the formerly failing case in 3.024 seconds; macOS passed 3/3. Digest-verified artifact receipts confirm 2,534/2,534 generic tests and 1/1 native gateway test, with zero failures, skips or other nonsuccess results. Authenticated main Windows and .NET logs contain no Xceed or Fluent Assertions warning.

Source head: 9a070c032ab20f14493d24f39c87cb0923c87502; tested PR merge: 135a13c80d3a84a864426041163b879f33ddba83; base: 3884d322c9548aed99886ef87854d37e21bac80f. The actual main merge and tested PR merge have identical Git trees.