No benchmarks for YAML serialization or code generation (implementation plan Task 8.1 not started) #117

What's missing

Plan: docs/implementation-plan.md L127–130. The same item appears in docs/design.md L236.

• Task 8.1: Performance optimization
  • Add benchmarks for core operations
  • Optimize serialization/deserialization
  • Implement caching where appropriate

What exists today

Nothing. The repository has no BenchmarkDotNet reference, no benchmark project and no timing tests. The plan's optimisation and caching steps have no measurements to justify them.

Why it matters

The editor regenerates the preview on every AST change (Coder.Editor/CoderEditorApp.cs, the preview pane). The YAML serializer and deserializer walk the tree by hand. Without a baseline, a regression in either one, or a quadratic path in a generator, would go unnoticed until the editor feels slow. The plan's optimisation step can't start until there's something to measure.

Acceptance criteria

• A benchmarks/Coder.Benchmarks project using BenchmarkDotNet. It lives under benchmarks/, following the org's naming convention so it isn't counted as a shipped deliverable.
• Benchmarks for YamlSerializer.Serialize, YamlDeserializer.Deserialize and Generate for each of the 7 registered generators, run over a representative AST such as the test exemplar (Coder.Test/Languages/CompiledExemplar.cs).
• Optimisation and caching (the plan's remaining bullets) come after this, and only where a benchmark shows a need. They are out of scope here.

Dependencies

None.