fix(agents): Add ids for reasoning messages and improve reasoning process to fix status 400 from openai

[tiginamaria]

Bugs:

• The ID of incoming reasoning messages was ignored, but it's required for outgoing messages. We generated it manually, but it didn't match the format rs_***, so we got 400 from OpenAI. The right approach here is to store the original ids of the reasoning messages
• For codex models, the reasoning is hidden, so we received empty text and summary, and while trying to send it back with the response, we also got 400 from OpenAI. The right fix here is to ignore empty reasoning, as it's hidden and makes no sense for the user.

Fixes:

• Add ids to reasoning messages
• Fix the reasoning messages response content, the text was ignored
• Ignore empty reasoning messages
• Add reasoning capability to control which models support reasoning

closes #1712
and bug reported in Slack https://kotlinlang.slack.com/archives/C08SLB97W23/p1773062179788829