InspectorTimingPhasesUi

Mirrors io.devconsole.network.NetworkTimingPhases without a sdk:network dependency. Every phase is legitimately null in normal operation -- a pooled connection does no DNS/connect, a plaintext request has no TLS, a cached response does no network work -- so a null phase must never be rendered as a zero-length bar; it must be omitted. All-null means no per-phase timing was captured for this transaction (an adapter that predates this field, or a transport that never wires up phase timing), in which case a caller should fall back to the total duration.