Scrub all remaining JasperFx.CodeGeneration usages from Marten

[jeremydmiller]

The follow-up to #4461 ("Removing All Runtime Compilation From Marten"). That PR retired the JasperFx.RuntimeCompiler PackageReference and the major emission pipelines, but called out a remaining cleanup:

ICodeFileCollection / ICodeFile implementations on DocumentStore, StoreOptions, and EventGraph are vestigial but harmless. Cheap follow-up to remove once we've confirmed no third-party Critter-Stack tool walks them.

This PR is that follow-up, plus the long-tail of stale using JasperFx.CodeGeneration imports, the now-orphaned GenerateCode(...) interface methods + override bodies, the [Obsolete] StoreOptions codegen-config properties #4461 left as no-ops, and the dead MartenSnapshot fingerprint feature that existed only to invalidate codegen artifacts that no longer exist.

Summary

Code changes (commit 1): 113 files, +60 / −3387 = ~3,300 LOC net deleted.

• 8 stale using JasperFx.CodeGeneration imports dropped — files had no actual type usage post-Removing All Runtime Compilation From Marten. (Boom) #4461.
• 3 dead interface methods removed: IIdGeneration.GenerateCode, ISelectableColumn.GenerateCode, plus UpsertArgument.GenerateCodeTo* / GenerateBulkWriterCodeAsync virtuals (and MetadataColumn.setMemberFromReader). Cascade-deleted the override bodies across 8 identity strategies, 9 upsert-argument derivatives, 13 metadata columns, plus DataColumn / IdColumn / Events/Schema/VersionColumn. The types themselves are preserved as data carriers / config markers.
• 5 whole-file deletions: Internal/CodeGeneration/MartenSnapshot.cs, MartenSnapshotInputs.cs, FrameCollectionExtensions.cs, StoreOptions.GeneratesCode.cs, Events/EventGraph.GeneratesCode.cs. Removed MartenSnapshot.VerifyAtBoot / PersistFingerprint calls from DocumentStore.cs and the two CoreTests covering them.
• ICodeFileCollection / ICodeFile implementations dropped from DocumentStore, EventGraph, and StoreOptions (carried implicitly through deleting the GeneratesCode partials). Removed 2 services.AddSingleton<ICodeFileCollection>(...) DI registrations from MartenServiceCollectionExtensions.cs.
• StoreOptions scrubbed: GeneratedCodeMode, SourceCodeWritingEnabled, GeneratedCodeOutputPath, AllowRuntimeCodeGeneration, SetApplicationProject, CreateGenerationRules, BuildFiles, _generatedCodeMode, PreferJasperFxMessage. Test-side cleanup deleted dozens of opts.GeneratedCodeMode = TypeLoadMode.X lines and several test files (e.g. CoreTests/Examples/CodeGenerationOptions.cs). ApplicationAssembly kept — AutoRegister and TryUseSourceGeneratedDiscovery legitimately need it as a scan hint.
• Directory.Packages.props orphan JasperFx.RuntimeCompiler PackageVersion removed. Comments referencing RuntimeCompiler scrubbed in SecondaryStoreProxyFactory.cs, CompiledQueryHandlerRegistry.cs, DocumentStore.CompiledQueryCollection.cs, Internal/ProviderGraph.cs.
• src/Marten/ is now free of JasperFx.CodeGeneration imports — grep -rn \"JasperFx\\.CodeGeneration\" src/Marten/ returns empty.

Doc changes (commit 2): 28 files, +108 / −148.

• docs/migration-guide.md updated to say the codegen-config knobs are deleted (not [Obsolete]).
• docs/configuration/cli.md Codegen warning reframed: dotnet run -- codegen write is no longer necessary for Marten; the codegen family stays exposed by the shared JasperFx CLI for tools like Wolverine that ship their own codegen.
• docs/configuration/aot-publishing.md and docs/configuration/optimized_artifact_workflow.md corrected the "kept as [Obsolete] no-ops" claim to "deleted entirely."
• docs/devops/devops.md Application-Dockerfile section dropped the RUN dotnet run -- codegen write step plus a Marten 9.0 tip. The recovered Docker content (the pre-9.0 multi-stage Dockerfile pattern) is captured in follow-up issues filed against Wolverine and JasperFx for re-publication in their docs.
• docs/schema/index.md lost the stale opts.GeneratedCodeMode = TypeLoadMode.Auto warning.
• All other docs/**.md changes are mdsnippets refreshes propagating the source-side scrubs from commit 1 (Startup.cs samples, hostbuilder snippets, ValueType / EventSourcing samples, etc.).

Test plan

• Full solution build: 0 errors, 13 warnings (pre-existing — unrelated to this PR's diff).
• CoreTests (net9.0): 411 pass, 1 skip, 0 fail.
• DocumentDbTests (net9.0): 987 pass, 1 skip, 0 fail.
• LinqTests (net9.0): 1257 pass, 1 skip, 0 fail.
• mdsnippets clean.
• markdownlint --disable MD009 clean across changed docs.
• cspell --config ./docs/cSpell.json clean.
• vitepress build docs exits 0.

Out of scope / follow-ups filed elsewhere

• Recovered Docker / codegen write content for Wolverine + JasperFx: filed as follow-up issues in those repos (see PR description trail).
• Test-project comments (Marten.AotSmoke, CompiledQueryTests, Marten.SourceGenerator.Tests) still reference JasperFx.RuntimeCompiler in code-comments only — left alone for a later AOT-publishing pass.
• MetadataColumn.GenerateCode virtual on the base class is gone, but a couple of MetadataColumn<T> subclasses (HeadersColumn, etc.) retain internal EventTableColumn-style codegen overloads they were never asked about in the inventory — out of scope here.

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