feat(multimodal): 视觉分层路由（多模态检测→主/视觉/OCR 工具）+ 语音 STT→TTS 降级链（异步）

internal/runtime/multimodal/voice/chain.go

@@ -0,0 +1,112 @@
+package voice
+
+import (
+	"context"
+	"fmt"
+
+	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
+)
+
+// Chain is a degrading provider list. STT and TTS walk the steps in order,
+// returning the first successful result and moving to the next step when a
+// provider is unavailable (nil direction) or fails. It implements STT and TTS so
+// it can be used anywhere a single provider is expected.
+type Chain struct {
+	steps []Provider
+}
+
+// NewChain builds a degrading chain from the given providers in the order they
+// should be tried. Passing a SilentProvider last guarantees the chain always
+// succeeds.
+func NewChain(steps ...Provider) *Chain {
+	return &Chain{steps: steps}
+}
+
+// STT walks the chain for a transcription.
+func (c *Chain) STT(ctx context.Context, audio Audio) (string, error) {
+	if len(c.steps) == 0 {
+		return "", ErrProviderFailed
+	}
+	var lastErr error
+	for _, p := range c.steps {
+		stt := p.STT()
+		if stt == nil {
+			continue
+		}
+		text, err := stt.STT(ctx, audio)
+		if err == nil {
+			return text, nil
+		}
+		lastErr = err
+	}
+	return "", fmt.Errorf("voice: %w: %v", ErrProviderFailed, lastErr)
+}
+
+// TTS walks the chain for synthesized audio.
+func (c *Chain) TTS(ctx context.Context, text string) (Audio, error) {
+	if len(c.steps) == 0 {
+		return Audio{}, ErrProviderFailed
+	}
+	var lastErr error
+	for _, p := range c.steps {
+		tts := p.TTS()
+		if tts == nil {
+			continue
+		}
+		audio, err := tts.TTS(ctx, text)
+		if err == nil {
+			return audio, nil
+		}
+		lastErr = err
+	}
+	return Audio{}, fmt.Errorf("voice: %w: %v", ErrProviderFailed, lastErr)
+}
+
+// Option customizes a chain built by New.
+type Option func(*chainConfig)
+
+// chainConfig carries the assembled steps for New.
+type chainConfig struct {
+	steps []Provider
+}
+
+// WithProviders overrides the provider steps assembled from config. Tests use it
+// to inject deterministic mock providers instead of the real adaptation-point
+// rungs.
+func WithProviders(steps ...Provider) Option {
+	return func(c *chainConfig) { c.steps = steps }
+}
+
+// New assembles a chain from cfg using the fixed degradation order
+// cloud → local → edge-tts/espeak → silent.
+//
+//   - cloud is included only when a cloud voice setting is present (today an
+//     API key) so a mis-configured build degrades quietly.
+//   - local is a pure adaptation point and is only included when supplied via
+//     WithProviders; by default it is skipped.
+//   - the edge-tts or espeak rung is included according to cfg.TTSProvider.
+//   - silent is always appended last so the chain never fails outright.
+//
+// opts may supply a fully assembled step list to override this mapping.
+func New(cfg config.VoiceConfig, opts ...Option) *Chain {
+	conf := &chainConfig{}
+	for _, o := range opts {
+		o(conf)
+	}
+	if len(conf.steps) > 0 {
+		return NewChain(conf.steps...)
+	}
+
+	steps := make([]Provider, 0, 5)
+	if cfg.DashscopeAPIKey != "" {
+		steps = append(steps, CloudProvider(newDashboardSTT(cfg), newDashboardTTS(cfg)))
+	}
+	switch cfg.TTSProvider {
+	case "edge-tts", "edge":
+		steps = append(steps, EdgeTTSProvider(newEdgeTTS()))
+	case "espeak":
+		steps = append(steps, EspeakProvider(newEspeak()))
+	}
+	steps = append(steps, SilentProvider())
+	return NewChain(steps...)
+}