Make ingredient parsing safe against live Mealie rewrites

Co-authored-by: Fizz <fizz@agents.famfallman.com>
Co-authored-by: fredamn76 <fredrik.fallman@gmail.com>
Signed-off-by: fredamn76 <fredrik.fallman@gmail.com>

tests/test_normalize.py

@@ -6,11 +6,16 @@ import pytest
 from mealie_mcp.normalize import (
     clean_title,
     find_english_leftovers,
+    food_matches_line,
     has_extraction_failure,
     ingredient_display_lines,
+    line_remainder,
     looks_mangled,
+    match_unit,
     normalize_for_parser,
+    same_line,
     slugify,
+    unit_token,
 )
 
 
@@ -97,3 +102,33 @@ class TestIngredientDisplayLines:
             ]
         }
         assert ingredient_display_lines(recipe) == ["2 dl grädde", "1 gul lök", "salt"]
+
+
+class TestParserStructureSafety:
+    def test_reads_the_written_unit_token(self):
+        assert unit_token("4,7 dl basmatiris") == "dl"
+        assert unit_token("1-1,5 msk fond") == "msk"
+        assert unit_token("salt") is None
+
+    def test_matches_instance_unit_by_abbreviation(self):
+        gram = {"id": "g", "name": "gram", "abbreviation": "g"}
+        assert match_unit("g", [gram]) == gram
+        assert match_unit("dl", [gram]) is None
+
+    def test_rejects_a_nearby_but_different_food(self):
+        assert food_matches_line("kycklinglårfilé", "800 g kycklinglårfilé")
+        assert not food_matches_line("kycklingfilé", "800 g kycklinglårfilé")
+
+    def test_builds_note_from_only_the_unstructured_remainder(self):
+        assert (
+            line_remainder(
+                "200 g körsbärstomater (i olika färger)",
+                "g",
+                "körsbärstomat",
+            )
+            == "(i olika färger)"
+        )
+
+    def test_same_line_ignores_only_whitespace(self):
+        assert same_line("3 dl  grädde", " 3 dl grädde ")
+        assert not same_line("3 dl grädde", "3 liter grädde")