fix(tests): purge theater/broken tests, fix Config argparse pollution, fix is_ad() false positive

PHASE 1 — STOP THE BLEEDING:
- Delete 6 theater/dead test files (empty stubs, skipped placeholders)
- Create root conftest.py to isolate Config/argparse from pytest sys.argv
- Rewrite test_feed_loop_continuation.py: replace inspect.getsource() theater
  with real DopamineEngine behavior tests
- Rewrite test_ad_detection.py: use existing XML fixtures instead of phantoms
- Rewrite test_false_positive.py: use verified fixtures, caught REAL bug

PRODUCTION FIX:
- Fix is_ad() false positive: regex \bad\b was matching 'Create messaging ad'
  in DM inbox. Changed to exact label matching (text/desc must BE the ad marker,
  not merely contain it)

Result: 34 FAILED + 4 ERRORS -> 0 FAILED, 178 PASSED, 3 SKIPPED

tests/conftest.py

@@ -0,0 +1,38 @@
+"""
+Root Test Configuration — Global Guards Against Environmental Pollution
+=======================================================================
+
+This conftest protects ALL tests from the #1 cause of mass failure:
+Config() constructor calling argparse.parse_known_args() which reads
+sys.argv (pytest's arguments) and crashes with SystemExit: 2.
+
+Every test directory inherits these fixtures automatically.
+"""
+
+import sys
+
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def _isolate_config_from_argparse(monkeypatch):
+    """Prevent Config() from reading sys.argv during tests.
+
+    Root cause: Config.__init__ calls self.parse_args() which calls
+    self.parser.parse_known_args(). In pytest, sys.argv contains
+    pytest flags like '--ignore=...' which argparse interprets as
+    Config arguments, causing SystemExit: 2.
+
+    Fix: Temporarily set sys.argv to a minimal list so argparse
+    doesn't choke on pytest's arguments.
+    """
+    monkeypatch.setattr(sys, "argv", ["test_runner"])
+
+
+# ═══════════════════════════════════════════════════════
+# Pytest Markers Registration
+# ═══════════════════════════════════════════════════════
+
+
+def pytest_configure(config):
+    config.addinivalue_line("markers", "live_llm: requires a running local LLM (Ollama)")