docs: Update Phase 0 with specific test fix requirements

Per ADR-012, Phase 0 now specifies:
- 5 tests to REMOVE (broken multiprocessing)
- 4 tests to FIX (brittle assertions)
- 1 test to RENAME (misleading name)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/test_routes_feed.py

@@ -115,15 +115,15 @@ class TestFeedRoute:
         assert f"max-age={cache_seconds}" in response.headers["Cache-Control"]
 
     def test_feed_route_streaming(self, client):
-        """Test /feed.xml uses streaming response (no ETag)"""
+        """Test /feed.xml uses cached response (with ETag)"""
         response = client.get("/feed.xml")
         assert response.status_code == 200
 
-        # Streaming responses don't have ETags (can't calculate hash before streaming)
-        # This is intentional - memory optimization for large feeds
-        assert "ETag" not in response.headers
+        # Cached responses include ETags for conditional requests
+        # (Phase 3 caching was added, replacing streaming for better performance)
+        assert "ETag" in response.headers
 
-        # But should still have cache control
+        # Should also have cache control
         assert "Cache-Control" in response.headers