feat: WP-0001 foundation + WP-0002 core extensions

WP-0001 — Foundation & GAAF Baseline
- SCOPE.md, ARCHITECTURE-LAYERS.md, contracts/ tree
- .claude/rules/ stubs filled (architecture, stack, boundary)
- 57 tests (pytest), pyproject.toml with ruff+mypy, CI workflow

WP-0002 — Core Extensions (FR-4 + FR-3)
- FR-4: BudgetTracker (thread-safe) + LLMBudgetExceededError +
  optional RunConfig.budget_tracker + enforcement in all adapters
- FR-3: async_execute_prompt on LLMAdapter ABC (asyncio.to_thread
  fallback) + native asyncio.create_subprocess_exec in ClaudeCodeAdapter

81 tests passing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,26 @@
+"""
+Shared pytest fixtures for llm-connect tests.
+"""
+
+import pytest
+
+from llm_connect.models import RunConfig, LLMResponse
+from llm_connect.adapter import MockLLMAdapter
+
+
+@pytest.fixture
+def run_config():
+    """Default RunConfig for tests."""
+    return RunConfig()
+
+
+@pytest.fixture
+def mock_adapter():
+    """MockLLMAdapter with a predictable response."""
+    return MockLLMAdapter(mock_response="test response")
+
+
+@pytest.fixture
+def sample_response():
+    """A minimal valid LLMResponse."""
+    return LLMResponse(content="hello", model="test-model")