Expand test coverage for contrib/components and core modules

## Problem

Currently, the project has limited test coverage with only **24 test files covering 151 source files** (~16% ratio).
Several critical areas have no test coverage at all:

- **`contrib/components/`**: 25 source files, 0 test files
- **`contrib/language_models/`**: 10 provider implementations, minimal integration tests
- **`components/game_master/`**: 15 files, only 4 test files
- **`environment/engines/`**: 4 engine implementations, 3 test files

## Impact

Low test coverage leads to:
- Increased risk of regressions when refactoring
- Difficulty ensuring new contributions work correctly
- Reduced confidence in production deployments
- Harder to validate bug fixes

## References

- Existing test patterns: `concordia/components/game_master/gm_components_test.py`
- Current test setup: `pyproject.toml` (pytest-xdist configured)
- Related: Issue #187 (code quality improvements)


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**I'm interested in working on this .** I can start with Phase 1 (contrib/components) and
gradually expand coverage across the codebase.

Start with the existing test pattern in concordia/components/game_master/gm_components_test.py and review pytest-xdist configuration in pyproject.toml. Begin with Phase 1, contrib/components, and add coverage for the 25 source files; done means the targeted tests run successfully and coverage is expanded beyond the current baseline.

Written by the indexing model from the issue text.