Fix DeepHashAccessor#[] and generate typed nested resource classes

[razor-x]

Motivation

• Fix a live bug where DeepHashAccessor#[] always returned nil and produced non-stable nested objects, and prevent response deserialization from aborting on invalid Ruby ivar names.
• Ensure memoized/converted errors/warnings are refreshed after update_from_response to avoid stale data.
• Provide static, documented nested resource types so nested properties have YARD docs and IDE autocompletion by generating BaseResource subclasses for nested objects and lists.
• Leave the top-level decision about stripping unknown response keys (P3) unchanged for a later, separate decision.

Description

• Corrected DeepHashAccessor: #[] now delegates to the generated singleton readers (accepting string or symbol keys) and create_accessor_methods now processes values once at construction to preserve identity. (lib/seam/deep_hash_accessor.rb).
• Hardened BaseResource deserialization to return nil from load_from_response(nil), skip response keys that cannot be valid instance variable names, added BaseResource#[] for bracket access, and introduced resource_accessor / resource_list_accessor DSL and conversion logic to instantiate typed nested resources when present. (lib/seam/base_resource.rb).
• Fixed stale memoization by resetting @errors_converted and @warnings_converted before delegating update_from_response in the resource support modules, and updated the emitted string literals used by the generator (codegen/lib/static-resources.ts → lib/seam/resources/resource_errors_support.rb and resource_warnings_support.rb).
• Implemented nested-class discovery in the Ruby code generator: added merge-properties helper and updated codegen/lib/layouts/resource.ts and codegen/layouts/resource.hbs so generated lib/seam/resources/*.rb now emit documented nested BaseResource subclasses and declare resource_accessor / resource_list_accessor usages; numerous generated resource files were refreshed accordingly.
• Added and updated specs to cover the fixes and generation: spec/deep_hash_accessor_spec.rb, spec/resources/base_resource_hash_spec.rb, and spec/resources/base_resource_spec.rb now assert bracket access, stable nested identity, nil handling for load_from_response(nil), skipping invalid attribute names, errors refresh on update, and that declared nested objects become generated typed resources.

Testing

• Ran the unit specs with bundle exec rspec for the modified suites and they passed (including spec/deep_hash_accessor_spec.rb, spec/resources/base_resource_spec.rb, and spec/resources/base_resource_hash_spec.rb).
• Ran the full test/lint/generation pipeline: npm run generate (generator run and idempotency check), rake lint, and rake test completed successfully after minor tooling fixes in the generator templates.
• Performed TypeScript checks with npm run typecheck and JavaScript lint/format (npm run lint / prettier) during generator development and fixed reported issues; note that the local Node runtime triggered an engine warning because it is older than the project dev engine requirement (this did not prevent generation in this environment).
• Verified that code generation is idempotent and that generated resource files now include nested typed classes and resource_accessor declarations as expected.

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Codex Task