phraser, mavend: read the fallbacks from the file (V-501)

The accessors are functions now, so the call sites that compared against one
literal compare against the entry instead: IsUnknownFallback and
IsSourcesFallback in the daemon tests, the entry key in the phraser tests. A
reworded variant no longer breaks a Go test.

The eval scores every variant on the persona checks the nudges already pass.

internal/phraser/failure_test.go

@@ -8,12 +8,28 @@ import (
 	"testing"
 )
 
+// isFallback — the text she says is picked from that entry's variants, so a test
+// pins the entry rather than the wording. Pinning one line would make editing
+// fallbacks_ru_v1.json break Go tests, which is the coupling this file removed.
+func isFallback(t *testing.T, key, sources, got string) bool {
+	t.Helper()
+	e, ok := DefaultFallbacks().file.Entries[key]
+	if !ok {
+		t.Fatalf("no fallback entry %q", key)
+	}
+	for _, v := range e.Variants {
+		if strings.ReplaceAll(v, "{sources}", sources) == got {
+			return true
+		}
+	}
+	return false
+}
+
 // A dead server must be distinguishable from bad phrasing. Both PhraseChat and
-// PhraseQuery keep the turn alive with canned text — ChatFallback, "не знаю.",
-// "вот что я нашла: …" — and every one of those is also a legitimate reply, so
-// the text alone cannot say which happened. The error is the only signal, and
-// before Vikunja #397 it was dropped: the talk scorer reported a full run with
-// zero errors off a server that answered nothing.
+// PhraseQuery keep the turn alive with canned text — and every one of those
+// lines is also a legitimate reply, so the text alone cannot say which happened.
+// The error is the only signal, and before Vikunja #397 it was dropped: the talk
+// scorer reported a full run with zero errors off a server that answered nothing.
 func TestPhrasingReportsTheFailureWithTheFallback(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "model not loaded", http.StatusServiceUnavailable)
@@ -22,19 +38,20 @@ func TestPhrasingReportsTheFailureWithTheFallback(t *testing.T) {
 	p := NewLLMPhraserAt(srv.URL, Config{})
 
 	cases := []struct {
-		name string
-		call func() (string, error)
-		want string
+		name    string
+		call    func() (string, error)
+		key     string
+		sources string
 	}{
 		{"chat", func() (string, error) {
 			return p.PhraseChat(context.Background(), "как дела", nil)
-		}, ChatFallback},
+		}, fbChat, ""},
 		{"knowledge", func() (string, error) {
 			return p.PhraseQuery(context.Background(), "кто написал войну и мир", nil)
-		}, "не знаю."},
+		}, fbQueryUnknown, ""},
 		{"evidence", func() (string, error) {
 			return p.PhraseQuery(context.Background(), "сколько воды я выпил", []string{"два литра"})
-		}, "вот что я нашла: два литра"},
+		}, fbQuerySources, "два литра"},
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
@@ -42,8 +59,8 @@ func TestPhrasingReportsTheFailureWithTheFallback(t *testing.T) {
 			if err == nil {
 				t.Fatalf("no error from a dead server; the scorer would count this as bad phrasing")
 			}
-			if got != c.want {
-				t.Errorf("fallback text = %q, want %q — the daemon still has to say something", got, c.want)
+			if !isFallback(t, c.key, c.sources, got) {
+				t.Errorf("fallback text = %q, want a %q variant — the daemon still has to say something", got, c.key)
 			}
 		})
 	}
@@ -63,8 +80,8 @@ func TestEmptyKnowledgeAnswerIsAnError(t *testing.T) {
 	if err == nil {
 		t.Fatal("an empty response scored as an answer")
 	}
-	if got != "не знаю." {
-		t.Errorf("fallback text = %q, want \"не знаю.\"", got)
+	if !isFallback(t, fbQueryUnknown, "", got) {
+		t.Errorf("fallback text = %q, want a %q variant", got, fbQueryUnknown)
 	}
 	if !strings.Contains(err.Error(), "empty") {
 		t.Errorf("error = %v; want it to name the empty response", err)