Registry view with element dialog; Elements and Connectors panels under diagrams

- .archify-registry opens in a new read-only custom editor (archify.registry,
  default): the file's elements as cards; click one for a dialog with its
  description, the defining line (opens the YAML) and the diagrams that use
  it (open on click); Show Source and Open Model work from the view
- the same dialog opens from the registry cards on the model page
- Archify's node index is titled Elements; a Connectors panel built from the
  SVG edges lists from → to with the label, highlights on hover and keeps the
  highlight on click; side by side in the bottom rail
- integration test for the registry view; docs and changelog

package.json

@@ -125,11 +125,11 @@
         },
         {
           "command": "archify.showSource",
-          "when": "archifyPreviewFocus || activeCustomEditorId == 'archify.htmlViewer' || activeCustomEditorId == 'archify.diagram'"
+          "when": "archifyPreviewFocus || activeCustomEditorId == 'archify.htmlViewer' || activeCustomEditorId == 'archify.diagram' || activeCustomEditorId == 'archify.registry'"
         },
         {
           "command": "archify.openModel",
-          "when": "archify.isDiagramSource || archifyPreviewFocus || activeCustomEditorId == 'archify.diagram'"
+          "when": "archify.isDiagramSource || archifyPreviewFocus || activeCustomEditorId == 'archify.diagram' || activeCustomEditorId == 'archify.registry'"
         }
       ],
       "editor/title": [
@@ -150,7 +150,7 @@
         },
         {
           "command": "archify.showSource",
-          "when": "archifyPreviewFocus || activeCustomEditorId == 'archify.htmlViewer' || activeCustomEditorId == 'archify.diagram'",
+          "when": "archifyPreviewFocus || activeCustomEditorId == 'archify.htmlViewer' || activeCustomEditorId == 'archify.diagram' || activeCustomEditorId == 'archify.registry'",
           "group": "navigation"
         },
         {
@@ -165,7 +165,7 @@
         },
         {
           "command": "archify.openModel",
-          "when": "archify.inModel && (archify.isDiagramSource || activeCustomEditorId == 'archify.diagram') && !notebookEditorFocused",
+          "when": "archify.inModel && (archify.isDiagramSource || activeCustomEditorId == 'archify.diagram' || activeCustomEditorId == 'archify.registry') && !notebookEditorFocused",
           "group": "navigation@60"
         }
       ],
@@ -182,7 +182,7 @@
         },
         {
           "command": "archify.showPreview",
-          "when": "resourceFilename =~ /(\\.archify|\\.(architecture|workflow|sequence|dataflow|lifecycle)\\.json)$/",
+          "when": "resourceFilename =~ /(\\.archify|\\.archify-registry|\\.(architecture|workflow|sequence|dataflow|lifecycle)\\.json)$/",
           "group": "zzz_archify@3"
         },
         {
@@ -244,6 +244,16 @@
         ],
         "priority": "default"
       },
+      {
+        "viewType": "archify.registry",
+        "displayName": "Archify Registry",
+        "selector": [
+          {
+            "filenamePattern": "*.archify-registry"
+          }
+        ],
+        "priority": "default"
+      },
       {
         "viewType": "archify.htmlViewer",
         "displayName": "Archify HTML Viewer",