test(tools): fix mocking for faster_whisper, Python 3.14 stat, and sy…

[CharlieKerfoot]

Problem

• Transcription tests fail on import when faster_whisper is not installed
• test_stat_oserror fails on Python 3.14 because Path.exists()/Path.is_file() no longer delegate to Path.stat()
• test_update_gateway_restart fails on non-Linux platforms because is_linux() isn't mocked

Fix

• Inject a sys.modules stub for faster_whisper in both transcription test files
• Simplify test_stat_oserror to patch Path.stat directly and assert the validation function returns an error (no call_count threshold)
• Mock is_linux → True in the gateway restart test

Testing

• All three test files pass on macOS with Python 3.14

[teknium1]

Thank you for the cross-platform test stabilization work. This is now superseded by current main.

• Current main has a stronger faster_whisper test stub, including a ModuleSpec to keep find_spec() safe during collection: tests/tools/test_transcription_tools.py:18-26 (d682f320b).
• The stat-error case is already version-independent by mocking Path.exists, Path.is_file, and the explicit Path.stat() call: tests/tools/test_transcription_tools.py:794-805 (d682f320b).
• The gateway restart test file this PR modifies has since been removed from current main.

Automated hermes-sweeper review.