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/scheduler/AGENTS.md

@@ -0,0 +1,22 @@
+# Scheduler agent guide
+
+## Mission
+Scheduler detects advisory/VEX deltas, computes impact windows, and orchestrates re-evaluations across Scanner and Policy Engine.
+
+## Key docs
+- [Module README](./README.md)
+- [Architecture](./architecture.md)
+- [Implementation plan](./implementation_plan.md)
+- [Task board](./TASKS.md)
+
+## How to get started
+1. Open ../../implplan/SPRINTS.md and locate the stories referencing this module.
+2. Review ./TASKS.md for local follow-ups and confirm status transitions (TODO → DOING → DONE/BLOCKED).
+3. Read the architecture and README for domain context before editing code or docs.
+4. Coordinate cross-module changes in the main /AGENTS.md description and through the sprint plan.
+
+## Guardrails
+- Honour the Aggregation-Only Contract where applicable (see ../../ingestion/aggregation-only-contract.md).
+- Preserve determinism: sort outputs, normalise timestamps (UTC ISO-8601), and avoid machine-specific artefacts.
+- Keep Offline Kit parity in mind—document air-gapped workflows for any new feature.
+- Update runbooks/observability assets when operational characteristics change.