Name normalization and dedupe

Add harness.Normalize (lowercase, fold accents, strip punctuation, drop
filler words, collapse whitespace), harness.Similar (token-set Jaccard
similarity, threshold 0.85) and a Deduper built from the Regulars, Quest
log, pending suggestions and passed names that answers IsDuplicate.

Maestro task: f046ec6c-dbe2-4b12-bc95-3081c07714eb

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ai/harness/dedupe_test.go

@@ -0,0 +1,97 @@
+package harness
+
+import "testing"
+
+func TestNormalize(t *testing.T) {
+	tests := []struct {
+		name, want string
+	}{
+		{"Easy Chicken Tikka Masala", "chicken tikka masala"},
+		{"  The   BEST homemade\tLasagna  ", "lasagna"},
+		{"A Quick, Simple Classic Chili Recipe", "chili"},
+		{"Tacos (beef)", "tacos beef"},
+		{"Mac-and-Cheese!", "mac and cheese"},
+		{"Shepherd's Pie", "shepherds pie"},
+		{"Shepherd’s Pie", "shepherds pie"},
+		{"Crème Brûlée", "creme brulee"},
+		{"Jalapeño Poppers", "jalapeno poppers"},
+		{"Paella à la Valenciana", "paella la valenciana"}, // "à" folds to the filler "a"
+		{"Smørrebrød", "smorrebrod"},
+		{"Bœuf Bourguignon", "boeuf bourguignon"},
+		{"Käsespätzle mit Weißwurst", "kasespatzle mit weisswurst"},
+		{"Cre\u0300me bru\u0302le\u0301e", "creme brulee"}, // decomposed accents
+		{"İskender Kebab", "iskender kebab"},
+		{"Pho 24", "pho 24"},
+		{"Easy Recipe", ""},
+		{"", ""},
+	}
+	for _, tt := range tests {
+		if got := Normalize(tt.name); got != tt.want {
+			t.Errorf("Normalize(%q) = %q, want %q", tt.name, got, tt.want)
+		}
+	}
+}
+
+func TestSimilar(t *testing.T) {
+	tests := []struct {
+		a, b string
+		want bool
+	}{
+		{"Easy Chicken Tikka Masala", "chicken tikka masala", true},
+		{"Beef Tacos", "Tacos (beef)", true},
+		{"Chicken tacos", "Fish tacos", false},
+		{"Spaghetti Bolognese", "spaghetti bolognese recipe", true},
+		{"Crème Brûlée", "creme brulee", true},
+		{"Jalapeño Poppers", "JALAPENO POPPERS", true},
+		{"Smørrebrød", "Smorrebrod", true},
+		{"Chicken Tikka Masala", "Chicken Tikka Masala Curry", false}, // 3/4
+		{"Tacos", "Fish tacos", false},
+		{"Pad Thai", "Thai Green Curry", false},
+		{"Easy Recipe", "The Classic", false}, // nothing left to compare
+		{"Recipe", "Chili", false},
+	}
+	for _, tt := range tests {
+		if got := Similar(tt.a, tt.b); got != tt.want {
+			t.Errorf("Similar(%q, %q) = %v, want %v", tt.a, tt.b, got, tt.want)
+		}
+		if got := Similar(tt.b, tt.a); got != tt.want {
+			t.Errorf("Similar(%q, %q) = %v, want %v", tt.b, tt.a, got, tt.want)
+		}
+	}
+}
+
+func TestDeduper(t *testing.T) {
+	d := NewDeduper(DedupeSources{
+		Regulars: []string{"Beef Tacos", "Spaghetti Bolognese"},
+		QuestLog: []string{"Chicken Tikka Masala"},
+		Pending:  []string{"Crème Brûlée"},
+		Declined: []string{"Shepherd's Pie"},
+	})
+	tests := []struct {
+		name string
+		want bool
+	}{
+		{"Tacos (beef)", true},                  // Regular
+		{"spaghetti bolognese recipe", true},    // Regular
+		{"Easy Chicken Tikka Masala", true},     // Quest log
+		{"creme brulee", true},                  // pending suggestion
+		{"The Best Shepherds Pie", true},        // declined
+		{"Fish tacos", false},                   // shares only "tacos"
+		{"Chicken Tikka Masala Curry", false},   // below the threshold
+		{"Jalapeño Poppers", false},             // new
+		{"Easy Recipe", false},                  // nothing left to compare
+		{"Spaghetti Carbonara", false},          // shares only "spaghetti"
+		{"Bolognese Spaghetti (Classic)", true}, // word order does not matter
+	}
+	for _, tt := range tests {
+		if got := d.IsDuplicate(tt.name); got != tt.want {
+			t.Errorf("IsDuplicate(%q) = %v, want %v", tt.name, got, tt.want)
+		}
+	}
+}
+
+func TestDeduperEmpty(t *testing.T) {
+	if NewDeduper(DedupeSources{}).IsDuplicate("Beef Tacos") {
+		t.Error("an empty Deduper reported a duplicate")
+	}
+}