tui_app_server: tolerate missing rate limits while logged out

[etraut-openai]

Summary

Fixes a tui_app_server bootstrap failure when launching the CLI while logged out.

Root cause

During TUI bootstrap, tui_app_server fetched account/rateLimits/read unconditionally and treated failures as fatal. When the user was logged out, there was no ChatGPT account available, so that RPC failed and aborted startup with:

Error: account/rateLimits/read failed during TUI bootstrap

Changes

• Only fetch bootstrap rate limits when OpenAI auth is required and a ChatGPT account is present
• Treat bootstrap rate-limit fetch failures as non-fatal and fall back to empty snapshots
• Log the fetch failure at debug level instead of aborting startup

[fcoury]

@etraut-openai code looks good, I have tested before/after the fix. Before I got the error message and after I got the login flow. LGTM!