Fix: generator crash when external constructor parameter names differ only by case

[carl-andersson-at-westermo]

Update: confirmed root cause found and fixed

I initially suspected a missing DevelopmentDependency packaging setting (still included below as a valid best-practice fix), but I got direct access to the downstream consumer's repository and was able to reproduce the exact crash locally and confirm the true root cause end-to-end.

Confirmed root cause

Roslyn's SourceProductionContext.AddSource compares hint names with StringComparer.OrdinalIgnoreCase (verified directly against dotnet/roslyn's GeneratorDriver.cs and its own test suite: Assert.Equal(expectedName, source.HintName, StringComparer.OrdinalIgnoreCase)), but GenerateCode's declarations/arrayDeclarations dictionaries used the default (ordinal, case-sensitive) comparer for their keys.

Those dictionary keys double as both the generated hint name and a valid C# identifier. In the downstream consumer's real codebase, two completely unrelated classes each take an external IContainer-typed constructor parameter:

• SessionFactory(..., IContainer lifeTimeScope)
• Engine(IContainer lifetimeScope)

Both are entirely valid, independent C# — case-sensitive identifiers are allowed to differ only by case. Both survived as separate entries in the case-sensitive dictionary, and each independently tried to become its own generated source file via context.AddSource. Roslyn's case-insensitive uniqueness check rejected the second one, throwing ArgumentException("...must be unique within a generator") and aborting the entire generator run for that compilation with zero output — producing the exact reported CS8785 warning and the cascading CS0234 (missing Generated namespace).

This is a long-standing latent bug — the affected dictionaries have used the default comparer since the project's very first commit — not something introduced by the recently-merged perf work. It was simply never previously triggered by two same-name-different-case identifiers landing in the same compilation.

Fix

Since a partial class's members can be split across any number of source files (or consolidated into one) with zero effect on the compiled result, declarations are now grouped by a case-insensitive hint name, and any colliding entries are merged into a single generated file instead of one AddSource call per dictionary key. This preserves every declaration — both differently-cased members are still generated and remain independently usable — rather than silently dropping one via a case-insensitive dictionary overwrite, or crashing the whole generator.

Validation

1. Full test suite: 91/91 passing, including two new regression tests (identical external-parameter names across injections, and names differing only by case).
2. Reproduced the exact crash live against the actual downstream consumer's real WeConfig.Application project — confirmed SessionFactory/Engine with lifeTimeScope/lifetimeScope are both reachable from the same compilation.
3. Patched the locally-cached analyzer DLL with this fix and rebuilt WeConfig.Application end-to-end: build now succeeds with 0 errors (previously failed with the reported CS8785/CS0234).

Also included: analyzer packaging best practice

FactoryGenerator.csproj never set <DevelopmentDependency>true</DevelopmentDependency>, the standard/documented setting for Roslyn analyzer/source-generator NuGet packages, which prevents the analyzer from flowing to a referencing project's own downstream consumers regardless of that project's own PrivateAssets setting. This wasn't the cause of this specific crash, but it's an unambiguously correct, low-risk improvement kept in this PR.