test: fix rate limiter cross-test contamination

Each importlib.reload(dev_api) re-applies @limiter.limit() decorators to
the shared slowapi Limiter singleton, accumulating stale registrations in
_route_limits. One real HTTP request then triggered N limit-checks (N =
reload count), exhausting per-hour budgets prematurely.

Fix: conftest.py autouse fixture resets both _storage and _route_limits
before each test, giving a clean slate regardless of prior reloads.

Also updates test_dev_api_prep.py client fixture to use monkeypatch to
clear DEMO_MODE + importlib.reload to get a fresh IS_DEMO module state
(prevents 403 bleed from test_demo_guard.py tests running first).

All 842 tests passing.

tests/conftest.py

@@ -0,0 +1,18 @@
+"""Shared pytest fixtures for the Peregrine test suite."""
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def reset_rate_limiter():
+    """Reset slowapi state before each test.
+
+    Each importlib.reload(dev_api) re-applies @limiter.limit() decorators,
+    accumulating stale registrations in _route_limits on the shared limiter
+    singleton. One real request then triggers N limit-checks (N = reload count),
+    exhausting per-hour budgets prematurely. Clearing both _storage and
+    _route_limits before each test gives each test a clean slate.
+    """
+    from scripts.rate_limit import limiter
+    limiter._storage.reset()
+    limiter._route_limits.clear()
+    yield

tests/test_dev_api_prep.py

@@ -5,11 +5,12 @@ from fastapi.testclient import TestClient
 
 
 @pytest.fixture
-def client():
-    import sys
-    sys.path.insert(0, "/Library/Development/CircuitForge/peregrine/.worktrees/feature-vue-spa")
-    from dev_api import app
-    return TestClient(app)
+def client(monkeypatch):
+    import importlib
+    monkeypatch.delenv("DEMO_MODE", raising=False)
+    import dev_api
+    importlib.reload(dev_api)
+    return TestClient(dev_api.app)
 
 
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