Add one-command Meeting Lab benchmark runner

Add a repository-native runner for reproducible Meeting Lab benchmark runs on machines without Codex.

The runner:

- validates normalized Whisper input and Meeting Context
- checks Ollama availability and the requested model
- rejects preloaded Ollama models by default for clean benchmarks
- supports an explicit --allow-loaded-models override
- uses the selected production configuration:
  - qwen3.5:9b
  - target_chars=4500
  - max_chars=5500
  - min_chars=2500
  - overlap_blocks=0
  - think=false
  - temperature=0
  - num_ctx=32768
- executes the complete current pipeline
- creates unique benchmark output directories
- preserves artifacts up to failure
- records runtime, environment and validation metadata
- writes working_protocol.md only when the renderer contract passes

Add focused mocked tests and Linux-first setup documentation for the AI-PC.
The runner does not include Whisper execution.

.gitignore

@@ -23,6 +23,7 @@ dist/
 .pytest_cache/
 .test-tmp/
 .test-tmp-root/
+tmp_run_meeting_tests/
 .coverage
 htmlcov/