MercureClient is a single-topic SSE subscriber: opens a long-lived GET
on the hub URL with the topic query and Accept: text/event-stream,
parses the line protocol into update(data, id) signals, and reconnects
with 1s→2s→…→30s exponential backoff on drop. Tracks lastEventId across
reconnects and sends it as Last-Event-ID so the hub can replay missed
messages — backing the "Sleep / wake" path in PLAN.md §3 *Edge cases*.
One client per topic by design; multi-topic aggregation is Phase 2.
RestClient.qml is a Promise-style XMLHttpRequest wrapper. Auto-attaches
an RFC4122-v4 Idempotency-Key to every non-GET request (PLAN.md §4 and
§7) so retries are safe by default. Maps application/problem+json error
bodies into structured rejections for downstream UI.
Standalone CMake build remains green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
