feat(docs): Add comprehensive documentation for Vexer, Vulnerability Explorer, and Zastava modules

- Introduced AGENTS.md, README.md, TASKS.md, and implementation_plan.md for Vexer, detailing mission, responsibilities, key components, and operational notes.
- Established similar documentation structure for Vulnerability Explorer and Zastava modules, including their respective workflows, integrations, and observability notes.
- Created risk scoring profiles documentation outlining the core workflow, factor model, governance, and deliverables.
- Ensured all modules adhere to the Aggregation-Only Contract and maintain determinism and provenance in outputs.

docs/modules/notify/resources/samples/notify-template@1.sample.json

@@ -0,0 +1,19 @@
+{
+  "schemaVersion": "notify.template@1",
+  "templateId": "tmpl-slack-concise",
+  "tenantId": "tenant-01",
+  "channelType": "slack",
+  "key": "concise",
+  "locale": "en-us",
+  "body": "{{severity_icon payload.delta.newCritical}} {{summary}}",
+  "description": "Slack concise message for high severity findings.",
+  "renderMode": "markdown",
+  "format": "slack",
+  "metadata": {
+    "version": "2025-10-19"
+  },
+  "createdBy": "ops:zoya",
+  "createdAt": "2025-10-19T05:00:00+00:00",
+  "updatedBy": "ops:zoya",
+  "updatedAt": "2025-10-19T05:45:00+00:00"
+}