Use a StateWithMeta wrapper struct with #[serde(flatten)] for merging
rig state with frontend meta, replacing the manual string manipulation.
Also add Serialize derive and skip_serializing_if to FrontendMeta.
https://claude.ai/code/session_01XzurkeuUmamBuhQwxVy7T4
Signed-off-by: Claude <noreply@anthropic.com>
Introduce DecodeHistory<T> alias for the repeated
Arc<Mutex<VecDeque<(Instant, Option<String>, T)>>> pattern (9 fields).
Also switch VChanAudioCmd channel senders from UnboundedSender to Sender
to prevent unbounded memory growth under backpressure.
https://claude.ai/code/session_01XzurkeuUmamBuhQwxVy7T4
Signed-off-by: Claude <noreply@anthropic.com>