test: add Docker-based system test infrastructure

Adds a complete pytest system test suite for the HoneyBiscuitWorkshop
CI/CD system:

- runner.sh: orchestrates build, Docker image creation, and test
  execution
- Dockerfile: Arch Linux-based test image with Python venv
- conftest.py: shared fixtures (baker_bin, run_baker, work_dir, llm_env)
- probes/: environment probes for checking users, files, packages,
  processes
- llm/: LLM-based log judgment system with caching for semantic test
  evaluation
- fixtures/: test configs and scripts for prebake, bake, and finalize
  stages
- test_prebake.py, test_bake.py, test_finalize.py: test suites for each
  pipeline stage

Also refactors finalize.yml.tmpl notification config to use a templates
system.

.gitignore

@@ -9,3 +9,12 @@ archived
 *.bak
 *.clean
 session*
+llm.env
+
+# System test artifacts
+tests/results/
+tests/__pycache__/
+tests/**/__pycache__/
+tests/.pytest_cache/
+tests/llm/.cache/
+*.pyc