Cursor 4.6 fast=false is not available

**Describe the bug**
UI doesn't enable Cursor 4.6 in non-fast mode, making it 2x as expensive if you don't care about speed.

**Steps to reproduce**
Go to agent harnesses, choose Cursor, click the model selection dropdown - you'll see only 4.5 or 4.6 fast=true.

**Expected behavior**
You should be able to set fast=false, probably the same applies to thinking levels.

What did you expect to happen?
Exactly what I said about

**Version and platform**
Find your version at the bottom of the Settings sidebar. Write "unknown" if you can't determine it.
- Buzz version: 0.5.14
- OS: macOS 15.7.7

**Logs / additional context**
Same pattern appears across various harnesses - Claude Code I believe has the same issues with thinking depth on Opus 5, perhaps on other ones as well.

Reproduce the issue from the agent harnesses screen by selecting Cursor and opening the model dropdown. Trace the model and fast-mode selection used there, then verify that Cursor 4.6 can be selected with fast=false and that the relevant thinking-level options remain consistent.

Written by the indexing model from the issue text.