Copilot instructions

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2applyTo: "src/libraries/Microsoft.Extensions.DependencyInjection*/**"
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5# Microsoft.Extensions.DependencyInjection — Folder-Specific Guidance
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7## Service Lifetime Correctness (D7)
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9- Use `TryAdd{Lifetime}` instead of `Add{Lifetime}` for default registrations to avoid overriding user-configured services
10- Scoped services must never be injected into singleton services (captive dependency) — the scoped service would live for the application lifetime
11- Transient IDisposable services are tracked by the container until scope disposal — prefer scoped lifetime for disposable services
12- Service registration order matters — later registrations of the same type override earlier ones unless `TryAdd` is used
13- Decorator patterns where inner and outer service share the same interface must guard against infinite recursion during resolution
14- Do not inject `IServiceProvider` broadly as a service locator — inject the specific service needed
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16## Service Resolution
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18- `ActivatorUtilities.CreateInstance` bypasses the container registration or factory for the type being created, but it still resolves constructor dependencies through the provided `IServiceProvider`, which can invoke factories for those dependencies
19- Singleton dependencies resolved lazily at first request must not cause response-time spikes — consider `ValidateOnStart`
20- Factory delegates (`Func<IServiceProvider, T>`) should follow established parameter ordering conventions
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22## Abstractions Package (D17)
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24- `IServiceCollection`, `IServiceProvider`, and related interfaces belong in `Microsoft.Extensions.DependencyInjection.Abstractions`
25- The concrete `ServiceProvider` and resolution engine belong in the implementation package
26- Moving types between abstractions and implementation is a breaking change
27- Package references must target correct and aligned versions across the dependency graph
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29## Thread Safety (D6)
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31- Singleton services are accessed concurrently by default — all singleton implementations must be thread-safe
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33## Trim & AOT (D14)
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35- Annotate service resolution that uses reflection with `[DynamicallyAccessedMembers]`
36- Ensure the DI container works correctly under NativeAOT — test with `PublishAot=true`
37- No new IL2xxx trim warnings without explicit justification
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39## Test Coverage (D10)
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41- Every bug fix includes a regression test; every new feature has happy-path and edge/error tests
42- Dispose behavior must be tested — verify resources are released and post-disposal operations throw `ObjectDisposedException`
43- Test captive dependency detection and resolution order across different registration patterns
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