feat(component2json): add integer-based resource handle serialization

[JMLX42]

Summary

Implements #601 - WIT resource type support for MCP tool calls.

• Add ResourceHandleTable for mapping integer handles to ResourceAny values
• Update val_to_json/json_to_val to accept handle table parameter
• Resources serialize to integers (not debug strings) and can be passed back to components via their integer handles
• Update schema generation to use "type": "integer" for resources
• Handle tables persist per-component in LifecycleManager, enabling multi-call workflows (open → read → close)

This enables wasi:filesystem workflows where file descriptors need to persist across multiple tool calls.

Test plan

• All existing unit tests updated and passing (46 tests in component2json, 92 in wassette)
• Doctest updated and passing
• README documentation updated

Disclosure

This PR was developed with assistance from Claude (Anthropic's AI assistant).

[Mossaka]

Thanks, this is much needed to get resource handles covered in component2json crate. This is a breaking change.

[Mossaka]

perhaps encapsulate this further into a serialize and a deserialize functions so that it doesn't expose internal implementation details like next_handle?

[JMLX42]

so that it doesn't expose internal implementation details like next_handle?

I'm not sure I understand the problem:

1. Fields are already private - external code cannot access next_handle
2. ResourceAny isn't serializable, so the table can't be persisted anyway
3. We could add custom serde support with opaque serialization if a use case arises

But maybe I'm just misunderstanding the question.

[JMLX42]

This is a breaking change.

Is component2json supposed to be a public API? If that's the case, we could keep the original signatures as backward-compatible wrappers, and add new *_with_handles functions:

  // Backward-compatible API (resources not preserved across calls)
  pub fn vals_to_json(vals: &[Val]) -> Value {
      vals_to_json_with_handles(vals, &mut ResourceHandleTable::new())
  }

  pub fn json_to_vals(value: &Value, types: &[(String, Type)]) -> Result<Vec<Val>, ValError> {
      json_to_vals_with_handles(value, types, &mut ResourceHandleTable::new())
  }

  // New API for resource handling
  pub fn vals_to_json_with_handles(vals: &[Val], handles: &mut ResourceHandleTable) -> Value {
      // current implementation
  }

  pub fn json_to_vals_with_handles(
      value: &Value,
      types: &[(String, Type)],
      handles: &mut ResourceHandleTable
  ) -> Result<Vec<Val>, ValError> {
      // current implementation
  }