fix(converters): resolve top-level oneOf/allOf/anyOf in tool schemas

[xy69]

Summary

Fixes Bedrock TOOL_SCHEMA_INVALID error when tools have oneOf, allOf, or anyOf at the top level of their input_schema.

Problem

OpenCode (and potentially other clients) send tools whose input schemas use JSON Schema composition keywords at the root level. Bedrock rejects these with:

tools.67.custom.input_schema: input_schema does not support oneOf, allOf, or anyOf at the top level (reason: TOOL_SCHEMA_INVALID)

Solution

Added _resolve_top_level_composition() that flattens these before sending to Kiro:

• anyOf/oneOf: picks the first object-type variant (or first if none is object)
• allOf: merges all variants into a single schema

Nested composition keywords are preserved — Bedrock only rejects them at the root.

Testing

• 8 new tests covering all resolution strategies and edge cases
• All 17 TestSanitizeJsonSchema tests pass
• Full suite: 1679 passed, no regressions

[cla-bot]

Thanks for the PR! 🎉

Before merge, we need a one-time CLA confirmation.
It confirms that you have the right to contribute this code and allow the project to use it.

Full CLA text:
https://github.com/jwadow/kiro-gateway/blob/main/CLA.md

Please reply once with:

I have read the CLA and I accept its terms

You need to write once, all further messages from me can be ignored.

[xy69]

I have read the CLA and I accept its terms

[ankitcharolia]

@xy69 could you give a try to this gateway: https://github.com/ankitcharolia/kiro-gateway

It works quite well with All AI harness and actively being developed. The most important thing is that it is ACP compliant