router: add NormalizeMatchText tests and property invariants (slice 9b)

17 tests covering: whitespace collapse, case folding, NFKC normalization,
punctuation preservation, mixed-script identifiers, ё passthrough, and
property invariants (idempotent, deterministic, never removes punctuation/
wake words/numbers, never mutates original).

Test-only foldYo helper proves ё→е is lossy (всё → все) without
exposing an unused production function.

Vikunja: #725

internal/router/boundary_test.go

@@ -7,19 +7,22 @@ import (
 )
 
 // TestNormalizedInputIsMinimalValueObject — the typed ingress boundary carries
-// text and source and nothing else. This test pins the shape so a future slice
+// text, match text and source. This test pins the shape so a future slice
 // cannot add fields without updating every construction site.
 func TestNormalizedInputIsMinimalValueObject(t *testing.T) {
-	input := NormalizedInput{Text: "привет", Source: InputSourceVoice}
+	input := NormalizedInput{Text: "привет", MatchText: "привет", Source: InputSourceVoice}
 	if input.Text != "привет" {
 		t.Errorf("Text = %q, want %q", input.Text, "привет")
 	}
+	if input.MatchText != "привет" {
+		t.Errorf("MatchText = %q, want %q", input.MatchText, "привет")
+	}
 	if input.Source != InputSourceVoice {
 		t.Errorf("Source = %q, want %q", input.Source, InputSourceVoice)
 	}
 	// Empty zero value is usable.
 	var zero NormalizedInput
-	if zero.Text != "" || zero.Source != "" {
+	if zero.Text != "" || zero.MatchText != "" || zero.Source != "" {
 		t.Errorf("zero value is not empty: %+v", zero)
 	}
 }