[Bug] Model switcher caches stale entitlement state for Fable 5 mid-session

Bug Description
Title: Switching back to Fable 5 mid-session falsely prompts to "set up usage credits" on Max plan

Body:

Environment:

• Claude Code v2.1.220
• macOS (Darwin 25.5.0)
• Plan: Max (20x), low session usage at time of bug
• Launched via a wrapper terminal, no --model flag on the launch command; model comes from settings.json

What happens:
A fresh session started on Fable 5 works fine. But if I switch to another model (e.g. Opus) via /model and then try to switch back to Fable 5, I get a blocking prompt titled "Switch to Fable 5?" stating that Fable 5 runs on usage credits and that usage credits are turned off, with options to set up usage credits or keep the current model.

This is wrong. Fable 5 is included in my Max plan (confirmed in the plan usage panel, which explicitly says "Fable 5 is still included with your Max plan. If you see a prompt to set up usage credits for it, restart Claude Code."). Switching back to Fable should not require or reference usage credits at all.

Expected:
Switching back to Fable 5 mid-session should behave the same as starting a session on Fable 5 — no usage-credit prompt, since it's included in the plan.

Actual:
The /model switcher appears to cache a stale entitlement state. Returning to Fable 5 re-reads that stale state and treats Fable as a credit-gated model with credits disabled, even though it's plan-included.

Workaround:
Restart Claude Code (as the plan panel itself advises). A fresh session comes up on Fable 5 with no prompt. The false prompt only occurs when switching away and back within a live session.

Repro:

1. On a Max plan, start a session on Fable 5 (no prompt).
2. /model → switch to a different model (e.g. Opus).
3. /model → switch back to Fable 5.
4. Observe the "usage credits are turned off" prompt.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.220
• Feedback ID: 79afdd01-cae5-42ad-8fdd-14f729d84207

Errors

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