Add exhaustive pytest test suite (240 tests, all modules) (#601)

* Add exhaustive pytest test suite with 240 tests covering all modules

Comprehensive test coverage for a codebase that previously had zero tests:
- 7 test files covering parsers (20 parsers), obfuscators (4), packers (2),
  planners (5), requirements (8), stockpile_svc, donut handler, and hook.py
- Lightweight fake objects in conftest.py shim all Caldera internals so
  tests run standalone without a Caldera server
- Config: pytest.ini, tox.ini, .pre-commit-config.yaml

* Address Copilot review feedback on exhaustive pytest coverage

- Replace all hardcoded /tmp/stockpile-pytest/ paths with repo-relative
  paths derived from Path(__file__).resolve().parents[1]
- Fix shutil.which patch target in test_service.py to use patch.object on
  the loaded module (stockpile_svc imports via 'from shutil import which')
- Replace fixed /tmp/ dirs in test_packers.py with pytest tmp_path fixture
- Make base64_jumble randomness test deterministic by patching random.choice
- Fix BaseParser.line shim in conftest to match real implementation
  (split on '\n', strip '\r', skip empty lines)
- Use monkeypatch.setitem for sys.modules injection in test_hook.py
- Move donut shim to a module-scoped autouse fixture in test_donut.py
- Remove contradictory --ignore=E501 from .pre-commit-config.yaml flake8 config

Author: deacon-mp

.pre-commit-config.yaml

@@ -0,0 +1,21 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.5.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+      - id: check-added-large-files
+
+  - repo: https://github.com/psf/black
+    rev: 24.2.0
+    hooks:
+      - id: black
+        args: [--check, --diff]
+        language_version: python3
+
+  - repo: https://github.com/PyCQA/flake8
+    rev: 7.0.0
+    hooks:
+      - id: flake8
+        args: [--max-line-length=120]

pytest.ini

@@ -0,0 +1,5 @@
+[pytest]
+testpaths = tests
+asyncio_mode = auto
+markers =
+    asyncio: mark a test as an asyncio coroutine