Add DP033 cross-assembly duplicate strategy key analyzer

[Skymly]

Summary

• Add DP033 (Error): reports when the same strategy key for the same contract is registered in multiple referenced provider assemblies (plugin-host scenario).
• Extend analyzer test harness with two-referenced-assembly + host compilation helper.
• Fix generic [RegisterStrategy<T>] attribute recognition via MetadataName matching.

Closes #108.

Test plan

• dotnet test tests/DesignPatterns.Analyzers.Tests (44 passed)
• Full solution build
• CI green on PR

---

Note

Medium Risk
New compile-time Error on multi-provider references can break existing hosts that relied on overlapping keys; scope is analyzer-only with no runtime behavior change.

Overview
Adds DP033 (Error) for plugin-host builds: when a compilation references multiple provider assemblies that both register the same strategy key for the same contract, the new CrossAssemblyRegistryKeyAnalyzer reports on each conflicting [RegisterStrategy] (single-assembly duplicates stay on DP003).

Supporting changes: TryGetContractTypeFromAttribute now reads the generic contract from type arguments first; IsRegisterStrategyAttribute matches via MetadataName so [RegisterStrategy<T>] is recognized reliably. Diagnostics/docs register DP033; plugin docs flip from “not implemented” to describing the analyzer; tests add a two-referenced-assembly + host harness and DP033 scenarios.

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Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Attribute match ignores declaring namespace
  • Updated strategy attribute matching to compare fully qualified DesignPatterns.Behavioral metadata names instead of short attribute names.

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Preview (3d8fb5c934)

diff --git a/DesignPatterns.Analyzers/StrategyAnalysisConstants.cs b/DesignPatterns.Analyzers/StrategyAnalysisConstants.cs
--- a/DesignPatterns.Analyzers/StrategyAnalysisConstants.cs
+++ b/DesignPatterns.Analyzers/StrategyAnalysisConstants.cs
@@ -14,9 +14,12 @@
             return false;
         }
 
-        return attributeClass.OriginalDefinition.MetadataName switch
+        var originalDefinition = attributeClass.OriginalDefinition;
+        var metadataName = originalDefinition.ContainingNamespace.ToDisplayString() + "." + originalDefinition.MetadataName;
+
+        return metadataName switch
         {
-            "RegisterStrategyAttribute" or "RegisterStrategyAttribute`1" => true,
+            RegisterStrategyMetadataName or RegisterStrategyGenericMetadataName => true,
             _ => false,
         };
     }

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[cursor]

Attribute match ignores declaring namespace

Low Severity

IsRegisterStrategyAttribute treats any attribute whose OriginalDefinition.MetadataName is RegisterStrategyAttribute or RegisterStrategyAttribute`1 as a DesignPatterns strategy registration. Elsewhere (IsKeyedRegistrationAttribute, UnregisteredStrategyAnalyzer, generators) matching uses the fully qualified DesignPatterns.Behavioral metadata names.

 

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[Skymly]

Summary

DP033 closes the plugin-host gap left by DP003: duplicate strategy keys are caught per assembly by the generator, but multiple referenced provider assemblies could still collide at runtime until this analyzer runs at compilation.

What looks good

• Compilation-scoped scan across referenced assemblies, grouped by contract FQN + key (not symbol identity), which matches how plugin providers are built.
• Generic [RegisterStrategy<T>] recognition via MetadataName — the right fix for metadata round-trips.
• Tests cover the happy conflict path, distinct keys, single-assembly duplicates (still DP003), and different contracts sharing a key.

Follow-ups (out of scope for #108)

• DP034 info/doc hint deferred per issue.
• User docs: DesignPatterns.Docs PR #8 adds the #dp033 anchor for IDE help links.

LGTM for merge.