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/eval/fallbacks_test.go

@@ -0,0 +1,40 @@
+package eval
+
+import (
+	"math/rand"
+	"strings"
+	"testing"
+
+	"github.com/kami/maven/internal/phraser"
+)
+
+// TestFallbackPersona scores every line in fallbacks_ru_v1.json on the persona
+// checks the nudges are already held to. These lines are heard out loud, and
+// they live in a JSON file now, so a reworded variant that says "рад" or "вы"
+// would otherwise reach him with nothing between it and the speaker.
+//
+// Only the persona checks run. Mood and topic belong to a nudge, and these are
+// not nudges: they are what she says when there is no answer.
+func TestFallbackPersona(t *testing.T) {
+	fb, err := phraser.LoadFallbacks(rand.NewSource(20260804))
+	if err != nil {
+		t.Fatalf("LoadFallbacks: %v", err)
+	}
+	persona := map[string]bool{
+		CheckLang: true, CheckFeminine: true, CheckHisGender: true,
+		CheckAddress: true, CheckCringe: true, CheckLength: true,
+	}
+	variants := fb.Variants()
+	if len(variants) == 0 {
+		t.Fatal("no variants — the file loaded empty")
+	}
+	for _, v := range variants {
+		// {sources} stands for his own notes and never carries persona of its own.
+		body := strings.ReplaceAll(v, "{sources}", "два литра")
+		for _, r := range RunChecks(Case{}, body, "neutral") {
+			if persona[r.Name] && !r.Pass {
+				t.Errorf("%q fails %s: %s", v, r.Name, r.Detail)
+			}
+		}
+	}
+}