Add deterministic article search to MCP

mcp_server.py

@@ -8,6 +8,7 @@ from rollcalc_mcp_tools import (
     analyze_transport_capacity_result,
     calculate_roll_diameter_result,
     get_article_result,
+    search_articles_result,
 )
 from transport_calculation import TransportPresetKey
 
@@ -26,6 +27,11 @@ def create_server() -> Any:
         """Resolve RollCalc article master data. article_number is text (including leading zeroes); optional article_name_hint preserves existing conflict and ambiguity checks."""
         return get_article_result(article_number, article_name_hint)
 
+    @server.tool()
+    def search_articles(query: str) -> dict[str, Any]:
+        """Use search_articles when the user identifies a RollCalc product by name, family, designation, or descriptive article text instead of an exact article number. Do not guess or invent an article number: results are deterministic candidates from the RollCalc article master data. For an exact article number, use get_article -> calculate_roll_diameter -> optionally analyze_transport_capacity. For a product name, use search_articles first. Only when total_matches is exactly 1 may you use that candidate's exact article_number and continue through get_article and the requested workflow. When multiple candidates are returned, do NOT select the first or highest-ranked candidate and do not calculate yet: present relevant candidates with their article numbers, distinguishing names, and production_site when supplied; ask the user which article number is intended, then stop until they select it. Ranking/order expresses relevance only and never authorizes automatic selection. If no candidate is returned, say that no matching RollCalc article was found, ask for a more specific designation or article number, and do not invent an article. production_site=Malaysia is descriptive metadata only: it does not imply Bentofix, Bento 2, or any production machine."""
+        return search_articles_result(query)
+
     @server.tool()
     def calculate_roll_diameter(
         roll_length_m: float | None = None,