build: PackageValidation baseline 0.4.1 → 0.5.0

[Chris-Wolfgang]

Post-release step for v0.5.0 (#393): moves PackageValidationBaselineVersion from 0.4.1 to 0.5.0, so pack now validates against the version that just shipped.

Refs #394. That issue has other items (D20-Dice release, alert-count check, branch cleanup), so this PR does not close it.

Verified

• NuGet flatcontainer index for wolfgang.trypattern lists 0.5.0 (checked just before opening this PR).
• Locally at this branch's head:
  • dotnet build -c Release -p:TreatWarningsAsErrors=true: 0 errors.
  • dotnet test: 11/11 test runs passed.
  • dotnet pack: succeeded, with PackageValidation run against 0.5.0.

Labelled no-changelog: this is build configuration with no consumer-visible effect.

🤖 Generated with Claude Code

[github-actions]

PR benchmarks vs base (2287886)

Thresholds: time > +20% and ≥ +1000 ns or allocations > +50% and ≥ +16 B (or any allocation ≥ 16 B where the base allocated none) trigger a gate failure (label perf-impact-acknowledged overrides).

Benchmark	Δ time	Δ alloc
Action_Success	-1.4%	0 (new)
Action_WithException	-1.0%	+0.0%
RunAsync_Action_Success	+4.7%	-0.1%
RunAsync_Action_WithException	-5.5%	+0.0%
RunAsync_Func_Success	-8.1%	+0.0%
RunAsync_Func_WithException	-2.4%	+0.0%
Run_Func_Success	+13.1%	+0.0%
Run_Func_WithException	+1.6%	+0.0%