#3576 [Engine] Strata 0.2.1: Local SVG preview fails and agent falsely reports success

说明

### Area
[GUI] (the desktop app)

### Desktop app, Terminal or source?
Desktop app (Windows, Linux or Mac)

### What happened
In Strata 0.2.0 on Windows, I asked the agent to create an SVG of a pelican riding a bicycle.

The agent reported successfully generating the file but failed to preview it:

- Direct `file://` access was blocked.
- The localhost preview at `http://127.0.0.1:8731/pelican-on-bicycle.svg` failed.
- The image-viewing tool also failed.

Despite these errors, the agent incorrectly stated: "I previewed it in a browser to confirm it renders correctly."

**Expected behavior:** The agent should successfully preview locally generated files using an authorized mechanism, or accurately report that verification was unsuccessful.

### Smallest steps or command that reproduce it
1. Launch Strata 0.2.0 on Windows.
2. Enter: "Create me an SVG of a pelican riding a bicycle."
3. Observe the failed preview attempts and the final success message.

### Reproduction status
Reproduced locally (observed once).

### Strata version
0.2.0

### Graphics card, memory and system
Windows. Exact GPU, VRAM, RAM and OS build not recorded for this reproduction.

### Model, size and settings
Not recorded.

### Logs
```
Error: Access to 'file:' protocol is blocked.
Attempted URL:
file:///C:/Users/Me/Documents/Strata/Workspace/pelican-on-bicycle.svg

Couldn't open the page:
http://127.0.0.1:8731/pelican-on-bicycle.svg
Failed
```

The issue was observed in the agent's tool trace. Detailed diagnostic logs were not collected.

Only SVG preview behavior was observed; other file types were not tested.

<img width="622" height="539" alt="Image" src="https://github.com/user-attachments/assets/fafcc6fb-c6f2-44b6-86c2-f4cbf893b6f3" />