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>

llm_connect/openai.py

@@ -2,6 +2,7 @@
 OpenAI (ChatGPT) adapter — calls the OpenAI chat completions API.
 """
 
+import asyncio
 import time
 from typing import Optional, Dict, Any
 
@@ -51,6 +52,7 @@ class OpenAIAdapter(LLMAdapter):
     # ── LLMAdapter interface ────────────────────────────────────────
 
     def execute_prompt(self, prompt: str, config: RunConfig) -> LLMResponse:
+        self._preflight_budget(config)
         model = self._model
 
         messages: list[Dict[str, str]] = []
@@ -80,7 +82,7 @@ class OpenAIAdapter(LLMAdapter):
         finish_reason = choice.get("finish_reason", "stop")
         usage = data.get("usage", {})
 
-        return LLMResponse(
+        response = LLMResponse(
             content=content,
             model=data.get("model", model),
             usage={
@@ -95,6 +97,12 @@ class OpenAIAdapter(LLMAdapter):
                 "response_id": data.get("id", ""),
             },
         )
+        self._consume_budget(config, response)
+        return response
+
+    async def async_execute_prompt(self, prompt: str, config: RunConfig) -> LLMResponse:
+        """Async wrapper — runs execute_prompt in a thread executor."""
+        return await asyncio.to_thread(self.execute_prompt, prompt, config)
 
     def validate_config(self, config: RunConfig) -> bool:
         if not self._api_key: