fix: preserve output error contract during initialization

## Problem

`parse_file()` initializes the output directory before entering its existing exception-handling block. If directory setup raises an `OutputWriteError`, the exception bypasses the documented CLI error envelope and exit code 40 path.

This affects current `main` at `c6478aae9ab50a13fc54c0599a0a459396c15b99` and release `0.0.5`.

## Minimal reproduction

```python
from pathlib import Path
from unittest.mock import patch

from hi_pdf_parser.errors import OutputWriteError
from hi_pdf_parser.runner import parse_file

with patch(
"hi_pdf_parser.runner.ow.prepare_output_dir",
side_effect=OutputWriteError("output denied"),
):
parse_file(Path("tests/fixtures/normal.pdf"), Path("out"), None)
```

## Actual behavior

`OutputWriteError` escapes `parse_file()`. `main()` does not catch `CliError`, so the exception reaches the caller; the CLI emits no error envelope or mapped return code.

## Expected behavior

`parse_file()` should return an error envelope with `error_type` `OUTPUT_WRITE_FAILURE` and exit code 40, matching `hi_pdf_parser.errors` and the handling already used for later write failures.

## Impact

Common output initialization failures such as permission errors or invalid destinations can produce no machine-readable error or mapped exit status, making automation unable to handle the documented output-failure contract.

## Suggested implementation

Include output-directory and file-handler initialization in the existing exception boundary, and make cleanup conditional when the handler was not attached. Add a regression test for initialization failure.

Start in hi_pdf_parser/runner.py by reading parse_file(), its existing exception boundary, and the later write-failure handling; then check the error definitions in hi_pdf_parser/errors.py. Add the regression test described by the reproduction for initialization failure. Done means the failure returns an OUTPUT_WRITE_FAILURE envelope and mapped exit code 40, with cleanup safe when no handler was attached.

Written by the indexing model from the issue text.