* fix: surface MCP server errors in admin UI instead of silent logging
get_server_status() hardcoded error="" — connection and refresh failures
were logged but never surfaced to the admin panel.
Added _last_error dict to MCPClientManager: set on failure (connect,
refresh, periodic refresh, notification handler), cleared on success,
cleaned up on remove. Read in get_server_status().
Admin UI: error tooltip on list row status span, error text in red
in detail modal per-node list. Schema already had the field.
6 new tests for error tracking lifecycle.
* feat: add turnstone_mcp_server_errors Prometheus gauge
Exposes the count of MCP servers currently in error state via
/metrics for alerting and reliability tracking.
* fix: address copilot review — sanitize error strings, clear on notification success
- Add _set_error() helper: strips newlines, truncates to 256 chars
- All error-setting sites now use _set_error() for consistent sanitization
- Notification handler clears _last_error on successful refresh (fixes
stale error for push-notification servers that skip _periodic_refresh)
Patrick Buckley
f5af4875ba