refactor(rules): split wpf.md into index + references

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

shared/rules/wpf/index.md

@@ -0,0 +1,34 @@
+# WPF Code Guidelines
+
+* Use modern C# and current .NET/WPF conventions.
+* Keep UI, application logic and domain logic clearly separated.
+* Prefer MVVM for non-trivial views.
+* Keep code-behind minimal.
+* Use code-behind only for view-specific behavior that does not belong in the ViewModel.
+* Avoid business logic in views.
+* Avoid direct service access from controls.
+* Keep dependencies explicit and testable.
+* Prefer composition over inheritance.
+* Avoid unnecessary abstractions and framework wrappers.
+* Follow the existing project architecture unless there is a strong reason to change it.
+
+## Safety Rule
+
+* The UI must remain responsive.
+* Do not block the UI thread with I/O or expensive CPU work.
+* Do not bypass validation or security controls for convenience.
+* Do not introduce hidden cross-thread access.
+* Prefer predictable, explicit and testable UI behavior.
+
+## Detailed guidance
+
+Read the matching reference file before working in that area:
+
+| Read this reference for... | ...this kind of work |
+| --- | --- |
+| `references/mvvm-and-binding.md` | MVVM, data binding, property change notifications, dependency/attached properties |
+| `references/commands-and-async.md` | Commands, async/threading, UI-thread work, events |
+| `references/collections-and-xaml.md` | Collections, virtualization, layout, XAML |
+| `references/resources-and-lifecycle.md` | Resources/styles, windows/dialogs, navigation, memory, images/media |
+| `references/security-and-errors.md` | Security, file/process access, error handling, logging, validation |
+| `references/architecture-and-quality.md` | Architecture, DI, testing, code quality, performance |