[BUG] /model menu shows stale label "Sonnet 4.6" for Sonnet 5 after switching

Description

After running /model claude-sonnet-5, the CLI confirms the switch:

Set model to Sonnet 5 and saved as your default for new sessions

But reopening the /model menu still shows the entry labeled "Sonnet 4.6" as the checked/active option — there is no "Sonnet 5" label anywhere in the menu. The confirmation message and the menu UI disagree on the model name.

Steps to reproduce

1. Run /model claude-sonnet-5
2. Observe confirmation: "Set model to Sonnet 5 and saved as your default for new sessions"
3. Run /model again to open the menu
4. Menu still lists the default option as "Sonnet 4.6" (checked), with no "Sonnet 5" entry

Expected

Menu label should match the model actually selected (either both say "Sonnet 4.6" or both say "Sonnet 5").

Environment

• CLI version: 2.1.198 (confirmed latest via npm view @anthropic-ai/claude-code version)
• OS: Linux (WSL2)

Impact

Confusing/misleading — users can't tell from the menu which model is actually active, and may believe the newer model isn't available even though the switch command accepted it.