4.1 routing quality + 4.4 persona prompt

- VoiceConfig: add QueryMinScore (default 0.55) + Persona config fields
- voice.go: remove queryMinScore const, wire from cfg.Voice.QueryMinScore
  as reactiveHandler field
- llmphraser.go: add Persona to Config, prepend to system prompts in
  chat and query paths (systemPrompt/querySystemPrompt methods)
- main.go: pass personaFromCfg into both phraser config blocks
- Makefile: add download-embedder target (Xenova/paraphrase-multilingual-
  MiniLM-L12-v2, ~90MB ONNX)
- AGENTS.md: document embedder model download + libonnxruntime setup
- server.go: fix pre-existing wg.Add vs wg.Wait data race using accept
  mutex. make test green, zero races across all 29 packages.

internal/config/config.go

@@ -189,6 +189,18 @@ type VoiceConfig struct {
 	// Default 0.35 if unset.
 	RouterThreshold float64 `json:"router_threshold,omitempty"`
 
+	// QueryMinScore — the note-recall confidence gate. Top cosine below this
+	// ⇒ "I don't know" instead of a guess. Tuned for the ONNX embedder (0.55);
+	// the HashEmbedder floor scores lexically and may never clear it. 0.55
+	// default if unset.
+	QueryMinScore float64 `json:"query_min_score,omitempty"`
+
+	// Persona — optional prompt prefix that tunes maven's character. Prepended
+	// to every LLM system prompt (nudge phrasing, note queries, general
+	// knowledge). Empty string ⇒ current hardcoded persona (feminine-gendered
+	// Russian self-reference). Example: "Be formal and answer in English only."
+	Persona string `json:"persona,omitempty"`
+
 	// Weather — the weather provider config. nil ⇒ the daemon wires
 	// the stub provider (returns ErrNotConfigured — "погода не настроена").
 	// Set provider to "open-meteo" to use the keyless Open-Meteo API.
@@ -309,6 +321,7 @@ const (
 	DefaultRepeatInterval   = 5 * time.Minute
 	DefaultAutotuneInterval = 10 * time.Minute
 	DefaultRouterThreshold  = 0.35
+	DefaultQueryMinScore    = 0.55
 	DefaultToolTimeout      = 30 * time.Second
 )
 
@@ -379,6 +392,9 @@ func (c *Config) applyDefaults() {
 		if c.Voice.RouterThreshold <= 0 {
 			c.Voice.RouterThreshold = DefaultRouterThreshold
 		}
+		if c.Voice.QueryMinScore <= 0 {
+			c.Voice.QueryMinScore = DefaultQueryMinScore
+		}
 		if c.Voice.ToolTimeout <= 0 {
 			c.Voice.ToolTimeout = Duration(DefaultToolTimeout)
 		}