Add machine-aware maximum product length

docs/architecture.md

@@ -48,6 +48,19 @@ warning. Line speed remains configured but is outside the initial roll-only
 scope. Flask and MCP are thin adapters; no machine constraints are duplicated
 in those layers or in browser code.
 
+`calculate_machine_max_product_length()` composes the same domains for target
+length questions. It resolves the machine only through `MachineRepository`,
+uses `calculate_product_length()` with the configured maximum diameter, and
+maps its average length to the nominal maximum and its minimum length to the
+conservative/no-warning maximum. Material-weight maxima use the shared
+`calculate_material_length_for_weight()` inverse; final material weights use
+`calculate_material_weight()`. The domain chooses governing constraints,
+including deterministic ties, and verifies selected lengths through the
+existing direct roll and feasibility services. It never resolves articles,
+reads YAML in adapters, duplicates roll mathematics, applies a manufacturing
+increment, or implements conditional production rules. Flask and MCP expose
+thin adapters; the browser UI remains unchanged.
+
 ## Constrained Natural-Language Flow
 
 ```text