Support .archify diagram files (0.2.0)

.archify files are Archify JSON diagram sources. They open as JSON,
preview with the same commands, report validation problems, and get
completion from a schema that dispatches on diagram_type. Adds a
hello.archify example and tests for detection, the dispatching schema
and the VS Code behaviour.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/sync-archify.mjs

@@ -60,6 +60,28 @@ for (const file of fs.readdirSync(path.join(skill, 'schemas'))) {
   fs.writeFileSync(path.join(schemaOut, file), `${JSON.stringify(schema, null, 2)}\n`);
 }
 
+// *.archify files carry their type only in diagram_type, so they get one
+// schema that dispatches to the per-type schema.
+const TYPES = ['architecture', 'workflow', 'sequence', 'dataflow', 'lifecycle'];
+const dispatcher = {
+  $schema: 'https://json-schema.org/draft/2020-12/schema',
+  title: 'Archify Diagram',
+  description: 'An Archify diagram source. diagram_type selects the schema that applies.',
+  type: 'object',
+  required: ['diagram_type'],
+  properties: {
+    diagram_type: {
+      enum: TYPES,
+      description: 'Kind of diagram: architecture, workflow, sequence, dataflow or lifecycle.',
+    },
+  },
+  allOf: TYPES.map((type) => ({
+    if: { properties: { diagram_type: { const: type } }, required: ['diagram_type'] },
+    then: { $ref: `${type}.schema.json` },
+  })),
+};
+fs.writeFileSync(path.join(schemaOut, 'archify.schema.json'), `${JSON.stringify(dispatcher, null, 2)}\n`);
+
 let revision = 'unknown';
 try {
   revision = execFileSync('git', ['-C', source, 'rev-parse', 'HEAD'], { encoding: 'utf8' }).trim();