* feat: add channel health diagnostics
* fix(channels): harden startup failure reporting
- sanitize operator-facing failure details instead of exposing raw upstream errors
- keep registered channel instances failed during reload/startup errors and clean up pre-registration failure entries
- stop Telegram warning states from reporting running=true after polling or startup failures
* feat(channels-ui): surface actionable health diagnostics
- expand channel and overview views with richer health summaries, remediation hints, and failure history
- refine the channel dashboard layout so diagnostics are easier to scan instead of reading a wall of text
- keep shared web and desktop channel types aligned with the new health payload
* fix(web): harden channel health diagnostics states
- treat enabled channels without backend status as checking instead of stopped\n- align fallback remediation and overview attention synthesis with channel reality\n- localize diagnostics copy and reject invalid channel detail tabs\n\nRefs #628\nRefs #633
* docs(pr-assets): add channel diagnostics visual review pack
Kai (Tam Nhu) Tran
4cd7b0a8d4