[Issacboy123]

Summary

This PR fixes OpenAI Responses requests that reject update_plan and agent_action because their parameter schemas use anyOf at the object root. Both tools now publish plain object schemas that remain valid after OpenAI payload conversion.

Reasoning

OpenAI does not accept composition keywords at the function-parameter root, so the schemas cannot express operation unions there. Plain object properties preserve provider compatibility, while runtime validation continues to enforce the exclusive update-or-clear and message-or-interrupt contracts.

Checking the serialized OpenAI payload and every built-in schema root covers the provider boundary where the failures occurred without making a real provider request or requiring credentials.

Changes

• Replaced the top-level anyOf schema with a plain object containing optional plan, clear, and explanation properties.
• Replaced the agent_action union with a plain object schema and preserved message and interrupt semantics in runtime validation.
• Added direct assertions that prohibited composition keywords are absent from the schema root.
• Added a mocked OpenAI Responses interaction that verifies the serialized tool schema remains compatible.
• Added coverage enforcing compatible roots across every built-in coding and subagent tool schema.

Testing

• node ../../node_modules/vitest/dist/cli.js --run test/update-plan-tool.test.ts test/tool-schema-compat.test.ts test/suite/subagent-actions.test.ts
• npm run check

[Pepps233]

lgtm; tested with deepseek & codex auth