Critical: iOS mobile UI uses expensive legacy models (Opus 4.1, Sonnet 4) instead of newer versions #471

Description

When forcing a model selection from the iOS mobile UI, Happy uses legacy expensive models instead of the current generation models.

Expected behavior:

• Selecting "Opus" should use: claude-opus-4.5 (model ID: claude-opus-4-5-20251101)
• Selecting "Sonnet" should use: claude-sonnet-4.5 (model ID: claude-sonnet-4-5-20250929)

Actual behavior:

• Selecting "Opus" uses: claude-opus-4.1 (significantly more expensive)
• Selecting "Sonnet" uses: claude-sonnet-4 (legacy model)

Impact

This is a critical issue because:

1. Cost impact: Opus 4.1 costs significantly more than Opus 4.5
2. No visibility: There's no way to know which model is actually active from the UI
3. Silent failure: The /model command produces no output, making it impossible to verify the active model
4. User expectation mismatch: Users expect to use the latest models when selecting a model tier

Environment

• Platform: iOS mobile UI
• Happy version: 1.5.0
• Device: iOS

Steps to Reproduce

1. Open Happy on iOS mobile
2. Force select a model (Opus or Sonnet) from the UI
3. The system uses legacy models instead of current generation
4. Run /model command - no output is shown to verify

Suggested Fix

1. Update model selection mapping to use latest model IDs:
   • Opus → claude-opus-4-5-20251101
   • Sonnet → claude-sonnet-4-5-20250929
2. Fix /model command to display output showing active model
3. Add UI indicator showing which model is currently active
4. Add release notes when model defaults change

Additional Context

This affects user trust and cost management, especially since there's no feedback mechanism to verify which model is actually being used.