fix(tui): SDD phase models configured directly in opencode.json show as [default] in Configure Models #2771

Pre-flight Checklist

• I have searched existing issues and this is not a duplicate
• I understand that PRs will be rejected if the linked issue does not have status:approved

📝 Bug Description

When SDD phase models are configured directly in opencode.json (e.g., by an AI agent setting agent.sdd-explore.model, agent.sdd-propose.model, etc.), the gga TUI "Configure OpenCode Models" screen does not reflect those assignments — all phases show [default].

OpenCode itself correctly picks up and uses the configured models at runtime for each SDD phase, confirming the config entries are valid.

What I did: I asked DeepSeek V4 Pro (via OpenCode) to choose the best cost/benefit models for each SDD phase and write them into my OpenCode config. It configured them in opencode.json under the agent map. I verified that each SDD phase (init, explore, propose, spec, design, tasks, apply, verify, archive, onboard) uses the right model at runtime.

What gga shows: Opening gga → "Configure OpenCode Models" shows every phase as [default], as if the config entries don't exist.

🔄 Steps to Reproduce

1. Configure SDD phase models directly in opencode.json (not through gga TUI). For example:

   {
     "agent": {
       "sdd-explore": { "model": "deepseek/deepseek-v4-pro" },
       "sdd-apply":   { "model": "deepseek/deepseek-v4-pro" }
     }
   }

2. Run gga
3. Go to "Configure Models" → "Configure OpenCode Models"
4. Observe the phase assignments

✅ Expected Behavior

The "Configure OpenCode Models" screen should load the model assignments from opencode.json (agent.<phase>.model) and display the actual configured provider/model for each phase, matching what OpenCode uses at runtime.

❌ Actual Behavior

All SDD phases show [default]. The models configured in opencode.json are not reflected.

Gentle AI Version

• gentle-ai: 2.3.0
• gga: 2.10.1

Operating System

Linux

AI Agent / Client

OpenCode

📋 Affected Area

TUI (terminal UI)

Additional Context

Looking at the code path:

• ReadCurrentModelAssignments() (internal/components/sdd/read_assignments.go:44) reads from opencode.DefaultSettingsPath() which resolves to ~/.config/opencode/opencode.json
• It extracts agent.<phase>.model for phases in configurableAgentSet
• This is called at internal/tui/model.go:2005-2007 when entering the Configure OpenCode Models screen, guarded by if m.Selection.ModelAssignments == nil

The user confirmed they use opencode.json (not .jsonc), so the file path should be correct. If the models are in agent.<phase>.model format with a provider/model separator (/ or :), ReadCurrentModelAssignments should pick them up.

Related but distinct issues: #771 (custom providers in .jsonc), #950 (wrong profile loaded by model screen).