mavttsd: a pronunciation dictionary, so she says the names right (V-458)

piper reads a Russian sentence with a Russian voice, and a Latin service id
inside it comes out spelled, mangled or read as if it were a Russian word:
"Vikunja", "SearXNG", "homesrv". The lever available is the text, so the
dictionary maps a name to how it should be spelled for the voice to say it,
and mavttsd applies it at the last edge before piper — every caller's text
passes through that one point, and nothing upstream has to know how a name
sounds.

Data, not code. deploy/tts-lexicon.json ships 29 names; adding one needs a
restart of mavttsd and no rebuild of the daemon that produced the text. Off
unless -lexicon is set, like every other optional capability, and a path that
is set and unreadable stops startup — saying names wrong in silence is the
failure it exists to remove.

Two details worth keeping: the alternation is sorted longest-first, or "Home
Assistant" reads as "Хоум Assistant"; and the boundaries are written out
rather than left to \b, which is ASCII-only and never fires next to a
Cyrillic letter.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/mavttsd/main_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/kami/maven/internal/audio"
+	"github.com/kami/maven/internal/tts"
 	"github.com/kami/maven/internal/worker"
 )
 
@@ -117,3 +118,18 @@ func abs(n int) int {
 	}
 	return n
 }
+
+// The dictionary that ships in deploy/ must parse and must be non-empty. It is
+// data, so nothing else would catch a trailing comma before the voice did.
+func TestShippedLexiconLoads(t *testing.T) {
+	lex, err := tts.LoadLexicon(filepath.Join("..", "..", "deploy", "tts-lexicon.json"))
+	if err != nil {
+		t.Fatalf("deploy/tts-lexicon.json: %v", err)
+	}
+	if lex.Size() < 10 {
+		t.Errorf("shipped dictionary holds %d names, want the full list", lex.Size())
+	}
+	if got := lex.Apply("задача в Vikunja"); got == "задача в Vikunja" {
+		t.Error("the shipped dictionary did not rewrite a name it lists")
+	}
+}