fix: close leaked file handles in sandbox_program_utils.py

[vominh1919]

Problem

In verifiers/v1/utils/sandbox_program_utils.py, there are 4 instances of json.loads(open(PATH).read()) which create file handles that are never explicitly closed:

• Line 372: json.loads(open(TOOL_DEFS_BY_PROTOCOL_PATH).read())
• Line 570: json.loads(open(RUNNER_CONFIG_PATH).read())
• Line 616: json.loads(open(TASK_PATH).read())
• Line 617: json.loads(open(STATE_INPUT_PATH).read())

These rely on garbage collection to close the file descriptors, which is unreliable — especially on alternative Python implementations (PyPy, GraalPy) where GC behavior differs from CPython.

Fix

Replace all 4 instances with json.loads(Path(PATH).read_text()), which:

1. Uses pathlib.Path.read_text() — the idiomatic Python 3 way to read files
2. Properly closes the file handle after reading (context manager internally)
3. Also adds from pathlib import Path import

Before vs After

# Before (file handle leaked)
defs = json.loads(open(TOOL_DEFS_BY_PROTOCOL_PATH).read())

# After (properly closed)
defs = json.loads(Path(TOOL_DEFS_BY_PROTOCOL_PATH).read_text())

Tests

This is a pure refactor with no behavioral change. All existing tests should continue to pass since Path.read_text() returns the same str that open().read() does.

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Note

Medium Risk
Touches the sandbox runner’s startup/config loading path; while intended as a no-op refactor, it changes how multiple JSON files are read and could break execution if imports/paths are incorrect.

Overview
Replaces several json.loads(open(PATH).read()) reads in sandbox_program_utils.py with Path(PATH).read_text() to ensure file handles are not leaked when loading tool defs, runner config, task, and state.

Adds a pathlib.Path import to support the new file-reading approach.

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