Summary

Two regressions surfaced in 2.2.0 when downstream consumers
(Wolverine 6.2.0, Marten 9.3.0 + a code-generating container that
inlines singletons) exercise the inline IEnumerable<T> codegen path.

• InputParserGenerator — the fallback converter expression emits
  FindConverter(typeof(T))! (Func<string, object?>) which can't bind
  to GeneratedFlag<T>'s Func<string, T> for nullable primitives like
  int? and DateTime?, producing CS1503 in the generated parser.
  Wrap with a cast (s => (T)…(s)), mirroring GetElementConverterExpression.

• DependencyGatherer — co-recursive yield iterators with no cycle
  protection. Frame⇄Variable graphs in real handlers cycle (or just go
  deep enough — ~250+ levels — to blow the stack). Rewrite both
  walks as a single iterative BFS with HashSet-tracked visited nodes.
  Preserve the original walk's side effect of populating the Variables
  cache so MethodFrameArranger.findInjectedFields (which reads
  Variables.Keys()) still sees every injected field — otherwise the
  generated handler class loses its _field declarations and the
  method body references undeclared identifiers (CS0103).

Bumps JasperFxVersion 2.2.0 → 2.2.1 (Fix). JasperFx.RuntimeCompiler
is independently versioned and untouched.

Originally included, now reverted

An earlier draft of this PR also rebound EnumerableSingletons.KeyedMirror's
factory to the source ServiceDescriptor directly (instead of
sp.GetServices(elementType).ElementAt(ordinal)) to break a stack
overflow seen with AddJasperFxEnumerableSingletonSupport() against a
Lamar container. That change broke
inline_enumerable_with_mixed_lifetimes.{two_singletons_among_mixed_are_each_shared, singleton_element_is_the_shared_container_singleton} in CI: for sources
registered as AddSingleton<T, Impl>() / AddSingleton<T>(factory), the
rebound factory built a fresh instance instead of returning the cached
non-keyed singleton, defeating the whole "mirror" contract.

The cycle is rooted in Lamar's ServiceFamily combining keyed and
non-keyed instances into one family per service type, so when
KeyedMirror's factory calls sp.GetServices(T), Lamar's
ListInstance.Elements includes the keyed mirror itself and Lamar
re-inlines it via InjectedServiceField.ToVariableExpression's
QuickResolve. MS DI's GetServices excludes keyed registrations, so
this is Lamar-specific. Will follow up separately.

Test plan

• CodegenTests.Services.inline_enumerable_with_mixed_lifetimes.* — 13/13 pass locally.
• CodegenTests full suite — 397/397 pass locally (net9 + net10).
• CommandLineTests full suite — 285/285 pass locally (net9 + net10).
• CI green on the test-codegen job and the four shipping projects
  (JasperFx, JasperFx.SourceGenerator, JasperFx.Events,
  JasperFx.Events.SourceGenerator).
• Manual: a NetCoreInput subclass with int? / DateTime? flag
  properties compiles via the input-parser generator.
• Manual: a Wolverine/Marten host whose WolverineRuntime ctor
  previously stack-overflowed in DependencyGatherer.findDependencies
  starts cleanly and runs a handler.

🤖 Generated with Claude Code