✅ Add demand check to product readiness validation

- Add demand > 0 check as first criterion in is_product_ready_for_optimization()
- Products with zero or negative demand now get exclusion reason: 'No demand or zero demand'
- Remove redundant demand <= 0 check from filter_products() loop
- Simplify filter_products() by consolidating all checks in is_product_ready_for_optimization()
- Update docstrings to reflect all 5 readiness criteria:
1) Positive demand
2) Correct product type
3) Line assignment
4) Staffing requirements
5) Production speed data
- Improve consistency and reduce code duplication

src/demand_filtering.py

@@ -124,17 +124,23 @@ class DemandFilter:
     
     def is_product_ready_for_optimization(self, product_id: str) -> Tuple[bool, List[str]]:
         """
-        Check if a product is ready for optimization.
-        1) Should be right type - standalone master, subkit, prepack
-        2) Should have line assignment
-        3) Should have staffing requirements
-        4) Should have production speed data
+        Check if a single product is ready for optimization.
+        1) Should have demand higher than 0
+        2) Should be right type - standalone master, subkit, prepack
+        3) Should have line assignment
+        4) Should have staffing requirements
+        5) Should have production speed data
         
         Returns:
             Tuple[bool, List[str]]: (is_ready, exclusion_reasons)
         """
         exclusion_reasons = []
         
+        # Check if product has positive demand
+        demand = self.demand_data.get(product_id, 0)
+        if demand <= 0:
+            exclusion_reasons.append("No demand or zero demand")
+        
         # Classify product type
         product_type, is_standalone_master = self.standalone_master_filter(product_id)
         
@@ -174,10 +180,8 @@ class DemandFilter:
     
     def filter_products(self) -> Tuple[List[str], Dict[str, int], List[str], Dict[str, int]]:
         """
-        Filter products into included and excluded lists.
-        1) Should have demand higher than 0
-        2) Should pass through is_product_ready_for_optimization()
-
+        Filter products into included and excluded lists based on optimization readiness.
+        Uses is_product_ready_for_optimization() to check all criteria.
         
         Returns:
             Tuple containing:
@@ -198,9 +202,6 @@ class DemandFilter:
         print("🔍 FILTERING DEMAND DATA FOR OPTIMIZATION")
         
         for product_id, demand in self.demand_data.items():
-            if demand <= 0:  # Skip products with no demand
-                continue
-                
             is_ready, exclusion_reasons = self.is_product_ready_for_optimization(product_id)
             
             if is_ready: