#34: God-class refactor, CI workflow, and quality rules

[Unthred]

Closes #34
Closes #32

Summary

• Split ProjectRuntime into ProjectRuntime.cs; ProjectOrchestrator.cs is now ~393 lines (was ~2,700)
• Extract TrayTooltipFormatter and BuildLifecycleFormatting (Core) plus BuildLifecycleToastNotifier; App.xaml.cs reduced ~155 lines
• Add ci.yml build+test on windows-latest for every PR
• Add commit-msg hook, PR issue-link workflow, board sync script (from Ops: Project board backlog sync and issue-linked commit enforcement #32)
• Add code-structure.mdc and strengthen testing.mdc (Tier 2 orchestration tests mandatory)
• InternalsVisibleTo for tests; fix BuildLogParserTests warning-count fixture

Refactor follow-ups

• ProjectRuntime.cs is still ~2,300 lines — next splits: build, run/watch, and test pipelines
• App.xaml.cs ~1,450 lines — tray menu builder is the next extraction candidate

Test plan

• dotnet build BuildMonitor.slnx -c Release
• dotnet test (111 passed)
• CI green on PR
• install-githooks.ps1 on other clones