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>

.claude/rules/stack-and-commands.md

@@ -1,19 +1,59 @@
 ## Stack
 
-<!-- TODO: Fill in language, frameworks, and key dependencies -->
-- **Language:**
-- **Key deps:**
+- **Language:** Python 3.10+
+- **Key deps (runtime):** `toml` (TOML config parsing)
+- **Key deps (dev):** `pytest`, `ruff`, `mypy`
+- **HTTP:** stdlib `urllib` via `_http.py` (no requests/httpx runtime dep)
+- **Build:** setuptools / uv
 
 ## Dev Commands
 
 ```bash
-# TODO: Fill in the standard commands for this repo
-
-# Install dependencies
+# Install (editable, with dev extras)
+uv pip install -e ".[dev]"
+# or
+pip install -e ".[dev]"
 
 # Run tests
+uv run pytest
+# or
+pytest
 
-# Lint / type check
+# Lint
+uv run ruff check .
 
-# Build / package (if applicable)
+# Type check
+uv run mypy llm_connect
+
+# Run a single test file
+uv run pytest tests/test_models.py -v
+
+# Build package (dry run)
+uv build --no-sources
+```
+
+## Project layout
+
+```
+llm_connect/         source package
+  adapter.py         LLMAdapter ABC + Mock/ErrorLLMAdapter
+  models.py          RunConfig, LLMResponse
+  exceptions.py      LLMError hierarchy
+  factory.py         create_adapter()
+  openai.py          OpenAIAdapter
+  gemini.py          GeminiAdapter
+  openrouter.py      OpenRouterAdapter
+  claude_code.py     ClaudeCodeAdapter
+  embedding_adapter.py  EmbeddingAdapter ABC
+  embedding_openai.py   OpenAICompatibleEmbeddingAdapter
+  embedding_cache.py    EmbeddingCache
+  embedding_factory.py  create_embedding_adapter()
+  toml_config.py     7-level TOML config resolution
+  config.py          LLMConfig, resolve_api_key, find_project_root
+  _http.py           shared HTTP POST utility
+  _token_estimator.py  rough token count estimate
+  similarity.py      cosine similarity utilities
+tests/               pytest test suite
+contracts/           GAAF-2026 contract docs
+workplans/           workplan files (LLM-WP-NNNN)
 ```