Add Archify | New Model… with three C4 examples and Open Model in the Explorer menu

- templates/models: C4 - Standard Web App, C4 - E-Shop, C4 - Event-Based
  Integration; each a complete model (main.archify, registry, context,
  containers, components) that validates
- archify.newModel: pick an example and a folder name, copy it, name the
  model after the folder, open the model page
- Explorer menu: New Model… on folders, Open Model on .archify and
  .archify-registry files; File → New File… lists New Model…
- unit test validates every example end to end; integration test runs the
  command; README, CHANGELOG, docs/model.md

templates/models/c4-event-based-integration/0300-components/router.archify

@@ -0,0 +1,46 @@
+schema_version: 1
+diagram_type: architecture
+meta:
+  title: Event router components
+  output: router.html
+components:
+  - ref: bus
+    pos: [40, 160]
+    size: [140, 60]
+  - id: validate
+    type: security
+    label: Validate
+    sublabel: schema check
+    pos: [270, 160]
+    size: [130, 60]
+  - id: enrich
+    type: backend
+    label: Enrich
+    sublabel: reference data
+    pos: [480, 160]
+    size: [130, 60]
+  - id: dispatch
+    type: backend
+    label: Dispatch
+    pos: [690, 160]
+    size: [130, 60]
+  - ref: store
+    pos: [920, 60]
+    size: [140, 60]
+  - ref: notifier
+    pos: [920, 160]
+    size: [140, 60]
+  - ref: dlq
+    pos: [270, 320]
+    size: [150, 60]
+boundaries:
+  - kind: region
+    label: Event router
+    wraps: [validate, enrich, dispatch]
+connections:
+  - { from: bus, to: validate, label: event }
+  - { from: validate, to: enrich, label: valid }
+  - { from: enrich, to: dispatch, label: enriched }
+  - { from: dispatch, to: store, label: append }
+  - { from: dispatch, to: notifier, label: notify }
+  - { from: validate, to: dlq, label: invalid, variant: dashed, labelDy: 24 }