docs: render architecture & flow diagrams as draw.io charts

Replace ASCII-art diagrams across the README and docs/ with editable
.drawio sources plus exported PNGs, so the diagrams render clearly in
rendered markdown and can be maintained/regenerated instead of being
hand-edited as fragile text art. Non-diagram blocks (code, folder
trees, UI wireframes) were left as text.

docs/plans/2026-05-29-native-alarms.md

@@ -16,23 +16,8 @@
 
 ## Task dependency overview
 
-```
-T1 ─┬─ T2 ─┬─ T17 (computed AlarmActor enrich)
-    │      ├─ T18 (proto) ── T19 (grpc mapping) ── T23 (DebugView)
-T3 ─┼─ T10 (DCL actor)
-    ├─ T11 (OPC UA adapter)
-    └─ T12 (MxGateway adapter)
-T4 ─┬─ T5 ── T6 ── T21 (mgmt handlers)
-    ├─ T7 (migration)
-    ├─ T8 ── T9 (validation)
-    └─ T20 ─┬─ T21 ── T26 (seed)
-            ├─ T22 (CLI)
-            ├─ T24 (template UI)
-            └─ T25 (instance UI)
-T13, T14 ──┐
-T1,T2,T3,T4(Resolved),T13,T14 ── T15 (NativeAlarmActor) ── T16 (InstanceActor wiring)
-(everything) ── T27 (docs) , T28 (integration/manual verify)
-```
+![native-alarms-task-dependency](diagrams/native-alarms-task-dependency.png)
+<!-- source: diagrams/native-alarms-task-dependency.drawio — edit, then re-export with export-drawio.sh -->
 
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