feat(rename): add session rename command

[Alex-duzhichao]

• Track the TUI's active session via tui.session.select events
• Add Server:update_session() using PATCH /session/:id
• Route session.rename and session.select through command() instead of the TUI
• Expose rename_session() on the public API

Tasks

• I read CONTRIBUTING.md
• I ensured my changes pass automated checks
• I reviewed and understand the AI-generated code in my changes (if any)

Description

Testing

1. Run :lua require("opencode").select() to open select picker
2. Select the session.rename
3. Change the session name

Related Issue(s)

Screenshots/Videos

[nickjvandyke]

Thanks for your contribution! This seems reasonable to include. Nice solution to track the active session. That's been an issue historically and I didn't think of this! I'll take a closer look when I get the chance.

Does OpenCode emit tui.session.select when a new session is created? Wondering if we need to track more events. Also wondering how to handle when we first connect to the server. I presume we can't get the session at that time, and must hide/disable the command.