* feat(channels): Channel.Send and MediaSender.SendMedia return delivered message IDs
Change Channel.Send signature from (ctx, msg) error to (ctx, msg) ([]string, error)
and MediaSender.SendMedia similarly, so callers can capture platform message IDs
for threading, reactions, and history annotation.
Adapters that return real IDs: Telegram (per-chunk MessageID), Discord (Message.ID),
Slack Send (ts), QQ (sentMsg.ID), Matrix (EventID). Slack SendMedia returns nil
because UploadFileV2 does not expose the posted message timestamp in its response.
All other adapters return nil IDs.
preSend and sendWithRetry in manager.go updated to propagate ([]string, bool).
README examples updated for both English and Chinese docs.
* style: apply golangci-lint fixes (golines)
* docs: fix Send migration guide — restore old error-only signature in before/after example
Phase 10: Define TypingCapable, MessageEditor, PlaceholderRecorder interfaces.
Manager orchestrates outbound typing stop and placeholder editing via preSend.
Migrate Telegram, Discord, Slack, OneBot to register state with Manager instead
of handling locally in Send. Phase 7: Add native WebSocket Pico Protocol channel
as reference implementation of all optional capability interfaces.
Define sentinel error types (ErrNotRunning, ErrRateLimit, ErrTemporary,
ErrSendFailed) so the Manager can classify Send failures and choose the
right retry strategy: permanent errors bail immediately, rate-limit
errors use a fixed 1s delay, and temporary/unknown errors use exponential
backoff (500ms→1s→2s, capped at 8s, up to 3 retries). A per-channel
token-bucket rate limiter (golang.org/x/time/rate) throttles outbound
sends before they hit the platform API.
Hoshina