v0.6.0 - Service-level connectivity tracking + passive failure-report endpoint

connectivity.py:
- Generalized 'spark' subject to any string; renamed 'spark' field to 'subject'
- Legacy v0.5 events with the old 'spark' field are migrated transparently on read (kind defaults to 'transition')
- New record_report(subject, ok, source, detail, latency_ms): always appends an event with kind='report'; does NOT mutate the current state (only active polling is authoritative)
- summary() returns events normalized to the new schema

Wiring:
- /api/status now calls record_state for vllm/parakeet/magpie (dedup on no-change)
- /api/services calls record_state for each service after its http check
- Result: dashboard observes service-level transitions automatically with no extra polling

Passive endpoint:
- POST /api/health-event with {service, ok, source?, error?, ms?}
- Useful for external apps (e.g. Open WebUI) to surface sub-poll-interval failures the dashboard would otherwise miss

UI:
- Connectivity dialog groups events by subject (hosts ordered first, then services)
- Per-subject summary shows transition count, down count, report count, failed-report count
- Transitions and reports render inline with distinct styling; reports show source app + error + latency
- Legacy v0.5 events render unchanged

Docs:
- README documents /api/health-event with a curl example

Package: bump to 0.6.0:0

README.md

@@ -84,6 +84,24 @@ Other services on your LAN can hit `GET /api/endpoints` to learn where the curre
 
 `base_url` is filled in whenever Configure Sparks has been completed (even if the underlying service isn't currently up). Pair the URL with `ready: true` to safely route traffic.
 
+## Reporting failures from external apps
+
+Spark Control polls every 5 s, so a brief blip in Parakeet/Magpie/vLLM availability can slip between polls and never make it into the connectivity log. To capture short failures, an external app (e.g. Open WebUI) can POST whenever a call fails (or succeeds):
+
+```bash
+curl -X POST http://<dashboard-url>/api/health-event \
+  -H 'content-type: application/json' \
+  -d '{
+    "service": "parakeet",
+    "ok": false,
+    "source": "open-webui",
+    "error": "HTTP 503",
+    "ms": 420
+  }'
+```
+
+Fields: `service` (required), `ok` (required), `source` (optional, free-form), `error` (optional), `ms` (optional latency). Each POST appends a `report` event to the connectivity log alongside the polling-based transition events.
+
 ## Status
 
 **v0.2.3** — installed and verified on a Start9 server. Five bundled LLMs in the catalog (qwen3-vl, gemma4, qwen36, qwen3-235b-fp8, qwen2.5-72b), plus any custom models added through the UI.