## Problem
With the new tasks data model, a task starts with an `initializing`
status. However, the API returns `current_state: null` to represent the
agent state, causing the frontend to display "No message available".
This PR updates `codersdk.Task` to return a `current_state` when the
task is initializing with meaningful messages about what's happening
during task initialization.
**Previous message**
<img width="2764" height="288" alt="Screenshot 2025-11-07 at 09 06 13"
src="https://github.com/user-attachments/assets/feec9f15-91ca-4378-8565-5f9de062d11a"
/>
**New message**
<img width="2726" height="226" alt="Screenshot 2025-11-12 at 11 00 15"
src="https://github.com/user-attachments/assets/2f9bee3e-7ac4-4382-b1c3-1d06bbc2906e"
/>
## Changes
- Populate `current_state` with descriptive initialization messages when
task status is `initializing` and no valid app status exists for the
current build
- **dbfake**: Fix `WorkspaceBuild` builder to properly handle
pending/running jobs by linking tasks without requiring agent/app
resources
**Note:** UI Storybook changes to reflect these new messages will be
addressed in a follow-up PR.
Closes: https://github.com/coder/internal/issues/1063
Susana Ferreira