chore(release): prepare the first stable release (2.0.0)

[kieronlanning]

Prepare ZodSharp for the first stable release (2.0.0)

Summary

Drops the prerelease tag for the first stable release, finalises the analyzer release tracking, resolves the
three public-surface decisions from the task, and syncs docs, READMEs, samples and tests.

This PR does not publish, tag or release anything. Merging to main triggers release.yml
(purview-release.yml, release-mode: NuGet), which tags v2.0.0 from package.json and publishes the four
packages. purview-build.json is unchanged (Release.Mode still None, no validation rule weakened).

Work item checklist

#	Item	Status
1	Move all unshipped analyzer rules to shipped	Done - ## Release 2.0.0 in AnalyzerReleases.Shipped.md carries ZODSGEN020, 021, 027-036, ZODSASP001/002/003/100/101; AnalyzerReleases.Unshipped.md keeps the standard Roslyn header and an empty new-rules table. All 35 IDs defined in DiagnosticLibrary.cs are tracked in exactly one file (ZODSGEN002, ZODSGEN022-026 remain intentional gaps). The tracking analyzer is live - a probe rule reported RS2000 as an error - so the clean build means zero RS2000/RS2001/RS2002/RS2007.
2	Bump the version to stable	Done - package.json is 2.0.0, just version prints 2.0.0, docs/wiki/Release-Flow.md describes the stable line. No stale 2.0.0-prerelease.* references remain.
3a	Empty FromJsonSchemaOptions public type	Done - type and options parameters removed from both packages.
3b	Duplicate public type names across the JSON packages	Done - import types moved into package-specific namespaces; coexistence test project added.
3c	External $ref in JSON Schema import	Done - limitation kept, message now names the unsupported reference; behaviour tested and documented.
4	Documentation in sync	Done - Guarantees-and-Limitations, JsonSchema-Import, JsonSchema-Export, SystemTextJson-Integration, NewtonsoftJson-Integration, AspNetCore-Integration (new ZODSASP diagnostics table), Source-Generator-Diagnostics (severity note + unused-ID gaps), Getting-Started, Cross-Platform-Interop, README.md and both package READMEs.
5	Samples and tests	Done - Examples.CLI and all samples/benchmarks build; new tests below; bun run test fixtures unchanged and green.
6	Validation	Done - see results below.

Section 3 decisions

Item	Decision	One-line rationale
3a	Remove the dead surface (FromJsonSchemaOptions + both options parameters)	Never ship an empty options type into a stable API; there is no near-term need for it.
3b	Eliminate the collision via package namespaces ZodSharp.JsonSchema.SystemTextJson / ZodSharp.JsonSchema.NewtonsoftJson (parser, serializer options, Z.FromJsonSchema host class)	The four identical full names disappear, so both packages can be referenced from one project without extern alias; the JSON integrations stay mutually exclusive by usage (import one package namespace per file).
3c	Keep the limitation, made actionable: NotSupportedException names the offending reference and explains how to resolve it	External $ref resolution needs IO/base-URI plumbing that does not belong in this release; the failure is now diagnosable and covered by tests in both packages.

Corrected keyword handling found while implementing 3c (86262af, revised in f0b3aee)

The $ref/$defs support that 3c builds on was effectively broken:

• There was no JSON property-name mapping for the keyword properties, so "$ref"/"$defs" in an authored
  JSON string were silently ignored (local $ref only ever worked for in-memory definitions, and
  ToJsonSchema wrote non-conformant ref/defs/schema/id names).
• The Newtonsoft reader consumed $ref as JSON metadata and deserialized such schemas to null, which
  made FromJsonSchemaParser.ConvertSchema throw NullReferenceException.

The final design keeps the shared POCO serializer-agnostic and gives each integration package ownership of
the JSON Schema keyword names:

• Purview.ZodSharp.SystemTextJson: a JsonSchemaNamingPolicy ($schema/$id/$ref/$defs, camelCase for
  everything else) used by both JsonSchemaSerializerOptions.Default and .Reading.
• Purview.ZodSharp.NewtonsoftJson: an equivalent naming strategy on the contract resolver, plus
  MetadataPropertyHandling.Ignore so $ref is no longer swallowed as metadata.
• JsonSchemaDefinition itself carries no serializer annotations, and a null sub-schema now fails with an
  actionable ArgumentException instead of a NullReferenceException.

Behaviour change to serialized JSON Schema output (it now matches the JSON Schema specification and this
repo's own documentation); the core POCO is unchanged apart from that guard, and purview-build.json
RequiredContent/ForbiddenContent are unaffected.

Tests added

• src/tests/JsonInterop.UnitTests/ - new project referencing both JSON packages: proves they compile
  together without extern alias, that the import types have distinct full names, and that each package's
  namespace binds Z.FromJsonSchema and its own serializer options type.
• SystemTextJson.UnitTests/Json/Schema/FromJsonSchemaParserTests.cs and the Newtonsoft equivalent - local
  $ref resolution, external $ref exception (type + message naming the reference), null-definition guard,
  JSON Schema keyword naming vs camelCase naming, and the new null-sub-schema failure.
• SourceGenerators.UnitTests/AnalyzerReleaseTrackingTests.cs - guards the shipped/unshipped files, the
  ## Release 2.0.0 section, the empty unshipped table and "one tracking entry per rule".
• ZodSharp.UnitTests/Core/MultiTargetingTests.cs - asserts the core assembly declares one of the supported
  target frameworks (net8.0/net9.0/net10.0) on every run.

Validation

Command	Result
just version	Current Version: 2.0.0
just lint-check	Checked 294 files - no formatting changes
just build	Build succeeded, 0 warnings / 0 errors (no RS2000/RS2001/RS2002/RS2007)
just test	1851 passed, 0 failed, 0 skipped across net8.0/net9.0/net10.0
just pipeline-pr	Pipeline Completed Successfully - 7 passed / 3 skipped (publish + GitHub release disabled); [PackValidation] Valid packages: 8/8; [Version] Package version: 2.0.0
just pipeline-pack-validate	Pipeline Completed Successfully (re-run after f0b3aee) - Valid packages: 8/8, Invalid packages: 0/8
bun run test	vitest cross-platform fixtures: 12 passed (1 file)

Pack inspection (artifacts/, all at 2.0.0):

• Purview.ZodSharp.2.0.0.nupkg: analyzers/dotnet/cs/Purview.ZodSharp.SourceGenerators.dll,
  buildTransitive/Purview.ZodSharp.props, lib/{net8.0,net9.0,net10.0}/Purview.ZodSharp.{dll,xml},
  purview-logo-light.png, README.md - exactly RequiredContent, and no
  analyzers/**/Purview.SourceGeneratorFramework.dll (ForbiddenContent).
• .snupkg symbol packages exist for all four packages (RequireSymbolPackage) and contain the per-TFM
  .pdb files (RequireSymbolFiles).

Notes / review points

1. 3b scope: the four colliding type names are separated, but the deserialize/serialize extension methods
   (DeserializeAndValidate, ValidateAndSerialize) intentionally remain in the ZodSharp namespace in both
   packages, matching the "mutually exclusive integrations" decision - importing both namespaces in one file
   still makes those calls ambiguous. Documented as a guarantee in Guarantees-and-Limitations.md.
2. Keyword naming ownership: after review feedback the keyword mapping lives in each integration package
   rather than as attributes on the shared POCO. Consumers who serialize JsonSchemaDefinition with their own
   serializer options get PascalCase names (as before), so use the package's JsonSchemaSerializerOptions for
   keyword-compliant output. f0b3aee carries the revision.
3. New JsonInterop.UnitTests project: added to src/ZodSharp.slnx; picked up by pipeline test discovery
   (*Tests.csproj under src/tests) with no purview-build.json change.
4. Commit hygiene: commitlint in this environment rejects the ! breaking-change shorthand (reports an
   empty type/subject), so 86262af marks the break with a canonical BREAKING CHANGE: footer instead.
   No hooks were bypassed.
5. Cross-platform fixtures were not regenerated because no Zod schema output changed.