Correct live-channel architecture; document dual-WebSocket design

Researched Directus's WebSocket subscription mechanism via context7 and
confirmed it only fires events for writes that go through Directus's
own ItemsService. Direct INSERTs from Processor are invisible to
subscribers. The previous claim in entities/directus.md that Directus
broadcasts Processor's writes was wrong.

New: wiki/concepts/live-channel-architecture.md captures the corrected
design with three options table, chosen-architecture diagram,
authorization flow, failure modes, multi-instance plumbing, scale
considerations, and open questions. Chosen path: Processor exposes its
own WebSocket endpoint for the high-volume telemetry firehose
(authentication via Directus-issued JWT, authorization delegated to
Directus once at subscribe time); Directus's built-in WebSocket covers
business-plane events. Each WebSocket serves the writes its plane
manages — preserves plane-separation and gives the gentlest failure
mode (Directus down only blocks new authorizations).

Updated:
- entities/directus.md — corrected the real-time-delivery section,
  added pointer to the new concept page.
- entities/processor.md — added Live broadcast section in
  responsibilities and a section explaining the dual-consumer-group
  plumbing for multi-instance HA.
- index.md — listed the new concept.
- log.md — synthesis entry for 2026-05-01 documenting the correction.

index.md

@@ -24,6 +24,7 @@ Content catalog for the TRM wiki. Maintained by the LLM on every ingest. See [[C
 - [[codec-dispatch]] — Flat registry keyed on codec ID; the seam that makes Phase 2 additive.
 - [[failure-domains]] — Independent component failure behavior; database is the only SPOF.
 - [[io-element-bag]] — The pass-through principle for model-specific telemetry inside AVL records.
+- [[live-channel-architecture]] — Dual-WebSocket design for live UX: Processor's endpoint for telemetry firehose, Directus's for business-plane updates.
 - [[phase-2-commands]] — Deferred design for server-to-device commands via Teltonika codecs 12/14.
 - [[plane-separation]] — Three-plane architecture (telemetry / business / presentation) split by data velocity and failure domain.
 - [[position-record]] — Boundary contract between vendor adapters and the rest of the system.