feat(capability): 转码能力包（vendor 纯 Go AMR-NB 解码器 + 黄金向量逐样本对照 + 8 哨兵 + 注册面）

internal/capability/transcode/amrnb/simd_noasm.go

@@ -0,0 +1,9 @@
+//go:build !amd64
+
+package amrnb
+
+// firRaw falls back to the portable implementation on non-amd64 targets.
+func firRaw(dst []int32, x []int16, coef []int16) { firRawGeneric(dst, x, coef) }
+
+// firDot falls back to the portable implementation on non-amd64 targets.
+func firDot(a, b []int16) int32 { return firDotGeneric(a, b) }