feat(log): add component supervision logging

[bartsmykla]

Motivation

When a component exits with an error or panics, the logs say nothing useful: no component name, no stack trace, no indication of whether the process is still running. On-call has to read the code to figure out which goroutine died.

Implementation information

Added runComponent, a supervision wrapper called from all three goroutine launch sites (non-leader start, runtime add, leader start). It:

• Logs component starting and component stopped as bookend info lines
• Recovers panics, logs the component name and stack trace, forwards the error to errCh
• Rate-limits panic logs per component name (10s window) to avoid log storms; the allowed log line includes a suppressed count so the operator can tell one crash from a cascade
• Uses non-blocking sends on errCh to avoid goroutine leaks after manager.Start returns; errCh is now buffered by 1 so the first error is never dropped even if a component panics before Start reaches its select

Added NamedComponent interface so components can provide a stable log name; falls back to %T otherwise.

The panic log level is Error (not double-logged at the manager level since the error is returned from Start). Normal exit errors are logged at Info for the same reason - the error is also returned from Start.