CodeBox.run_script() reads from host filesystem, not from inside VM

## Description

`run_script(path)` reads the script file from the **host** filesystem, not from inside the VM. This is counter-intuitive and undocumented — the docs show a pattern of creating a file inside the VM and then running it with `run_script()`, which fails.

## Reproduction

```python
import asyncio
import boxlite

async def main():
async with boxlite.CodeBox() as codebox:
# Create a script inside the VM
await codebox.run("""
with open('/tmp/analysis.py', 'w') as f:
f.write('import json\\nprint(json.dumps({"status": "ok"}))\\n')
""")
# Try to run the script from VM path
result = await codebox.run_script("/tmp/analysis.py")
print(result)

asyncio.run(main())
```

## Expected

`run_script("/tmp/analysis.py")` runs the script that was created inside the VM.

## Actual

```
FileNotFoundError: [Errno 2] No such file or directory: '/tmp/analysis.py'
```

The error occurs on the **host** side, confirming `run_script()` tries to read from host filesystem.

## Environment

- boxlite 0.5.10
- macOS Apple Silicon
- Python 3.12

## Suggested fix

Either:
1. Make `run_script()` read from inside the VM (consistent with the name), or
2. Clearly document that `run_script()` reads from the host and sends content to the VM for execution

Start at the CodeBox.run_script() API and reproduce the failure with the Python example in this issue. Determine the intended host-versus-VM path contract, then update the relevant implementation, documentation, and tests so the chosen behavior is verified.

Written by the indexing model from the issue text.