feat: add endpoints to delete and update message parts

[remorses]

Adds PUT and DELETE endpoints for message parts to enable custom compaction algorithms.

• PUT /session/:sessionID/message/:messageID/part/:partID - update a part's metadata
• DELETE /session/:sessionID/message/:messageID/part/:partID - delete a part

My use case is implementing a cli to delete wasteful tool calls from a session, custom compaction

I ran the script to re generate the SDK because the CI script that is supposed to do that was failing