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-channel@1.sample.json

@@ -0,0 +1,32 @@
+{
+  "schemaVersion": "notify.channel@1",
+  "channelId": "channel-slack-sec-ops",
+  "tenantId": "tenant-01",
+  "name": "slack:sec-ops",
+  "type": "slack",
+  "displayName": "SecOps Slack",
+  "description": "Primary incident response channel.",
+  "config": {
+    "secretRef": "ref://notify/channels/slack/sec-ops",
+    "target": "#sec-ops",
+    "properties": {
+      "workspace": "stellaops-sec"
+    },
+    "limits": {
+      "concurrency": 2,
+      "requestsPerMinute": 60,
+      "timeout": "PT10S"
+    }
+  },
+  "enabled": true,
+  "labels": {
+    "team": "secops"
+  },
+  "metadata": {
+    "createdByTask": "NOTIFY-MODELS-15-102"
+  },
+  "createdBy": "ops:amir",
+  "createdAt": "2025-10-18T17:02:11+00:00",
+  "updatedBy": "ops:amir",
+  "updatedAt": "2025-10-18T17:45:00+00:00"
+}