docs: add module documentation in AsciiDoc with PlantUML diagrams

Generated by per-group subagents covering all 52 modules across:
core (18), infrastructure (10), apps (5), interfaces (3),
plugins (7), testing (9)

Documentation format:
- AsciiDoc (.adoc) files in docs/modules/<group>/
- PlantUML (.puml) files in docs/diagrams/
- .adoc files reference diagrams via include:: directives

Each doc covers: purpose, responsibilities, non-responsibilities,
key types, event flow, integration points, invariants, PlantUML
diagram, known issues, and open questions.

docs/modules/infrastructure/infra-scheduler.adoc

@@ -0,0 +1,54 @@
+= infra-scheduler
+
+== purpose
+
+Placeholder module reserved for task scheduling infrastructure — delayed execution, cron-like triggers, and queue management. Currently contains only a `Module` marker object with no implementation.
+
+== responsibilities
+
+* Intended: schedule delayed or periodic task execution
+* Intended: manage execution queues and worker pools
+* Intended: persist scheduled tasks across restarts
+
+== non-responsibilities
+
+* Does not define scheduling contracts — that belongs to `core`
+* Does not implement workflow orchestration — that belongs to `core:kernel`
+* Does not provide inference routing — that belongs to `core:inference`
+
+== key types
+
+=== Module
+* **kind**: object
+* **purpose**: Module marker for the Gradle subproject; no behavior.
+
+== event flow
+
+*None.* No events are consumed or emitted. This is a placeholder.
+
+== integration points
+
+No integration points. The module has no dependencies beyond `core:events`.
+
+== invariants
+
+None — module is empty.
+
+== PlantUML diagram
+
+[plantuml, infra-scheduler, "png"]
+----
+include::../../diagrams/infra-scheduler.puml[]
+----
+
+
+
+
+== known issues
+
+Module is a placeholder — no scheduler infrastructure exists.
+
+== open questions
+
+* Will scheduling be event-driven (e.g., timer events) or time-based (cron)?
+* Should scheduling be embedded (coroutine-based) or backed by an external queue (Kafka, RabbitMQ)?