bug: task-level Cline model picker can initialize or persist the wrong model #469

Bug Description

When task-level Cline settings partially override the workspace defaults, the task detail model picker can initialize or persist the wrong model. This manifests as:

• A task showing one model in the picker but launching with another
• A model change from one task bleeding into another task

Environment

• OS: Linux (reproducible on all platforms — this is a web-ui React bug)
• Agent: Cline (any version using the Kanban web UI)

Steps to Reproduce

1. Configure a global Cline provider/model (e.g. Anthropic with claude-sonnet-4.6).
2. Open or create a task that either:
   • has only providerId overridden at task level (no explicit modelId), or
   • is still inheriting workspace Cline settings — then change the model from the task detail/chat panel picker.
3. Switch between multiple tasks with different providers/models, or start them in parallel.

Expected Behavior

• A provider-only task override should use that provider's default model.
• Changing the model from an existing task's chat panel should create or update task-specific Cline settings, not global settings.
• Multiple tasks should retain their own provider/model selections independently.

Actual Behavior

• The task can initialize from the global model instead of the overridden provider's default.
• The task detail/chat picker can update global Cline settings instead of the current task.
• This makes it look like a task is using a model from another task or from the last task you touched.

Root Cause

Two issues in the web-ui:

1. getInitialTaskModelId fell through to the global effective provider model when a task had only a providerId override.
2. ClineAgentChatPanel.persistClineModelSettings only wrote task-level overrides when taskHasExplicitClineSettings was already true, falling back to global settings for inherited tasks.