Phase 5: voice consistency pass

Tier-1 voice-consistency pass: whole-document LLM review surfacing passages
that read tonally out of place (formal/over-polished/paraphrased-too-closely),
as honey-decorated `voice` flags with no correction (awareness-only).

- internal/llm/voice.go: RunVoice sends the whole document (no TruncateDoc),
  MaxTokens 2048, 20s per-doc floor (VoiceInterval). Standalone voice prompt
  in prompts.go (not bundled with the grammar checkpoint, per spec).
- internal/suggestions: POST /api/docs/:id/voice. replacePending is now
  family-scoped (pendingScope) so grammar and voice never clobber each other's
  pending flags; both passes return the unified pending set. check/voice share
  one runPass helper. TestVoicePassCoexists covers both directions.
- Frontend: api.voiceDoc, useCheckpoint voicing/runVoice, honey "Check my
  voice" toolbar pill, breathing honey dot in StatusBar.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

internal/suggestions/chat_test.go

@@ -41,7 +41,7 @@ func TestAskPetalChat(t *testing.T) {
 		checkpoint: `{"suggestions":[{"original":"I has","replacement":"I have","explanation":"subject-verb agreement","type":"grammar"}]}`,
 		tokens:     []string{"Because ", "\"I\" ", "takes ", "\"have\"."},
 	}
-	srv, docID := newTestServer(t, client)
+	srv, docID, _ := newTestServer(t, client)
 
 	// Seed one suggestion via the checkpoint route, then grab its id.
 	do(t, srv, http.MethodPost, "/docs/"+docID+"/check", "")
@@ -102,7 +102,7 @@ func TestAskPetalChat(t *testing.T) {
 
 func TestAskPetalChatNotFound(t *testing.T) {
 	client := &streamClient{checkpoint: `{"suggestions":[]}`}
-	srv, _ := newTestServer(t, client)
+	srv, _, _ := newTestServer(t, client)
 	rec := do(t, srv, http.MethodPost, "/suggestions/does-not-exist/chat",
 		`{"messages":[{"role":"user","content":"hi"}]}`)
 	if rec.Code != http.StatusNotFound {