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/diagrams/app-cli.puml

@@ -0,0 +1,19 @@
+@startuml
+actor User
+participant CLI
+participant "Server\n(REST)" as REST
+participant "Server\n(WS)" as WS
+
+User -> CLI: correx run --workflow wf.toml
+CLI -> REST: POST /sessions {workflowId}
+REST --> CLI: sessionId
+CLI -> WS: ws /sessions/{id}/stream
+loop until SessionCompleted/Failed
+  WS --> CLI: StageStarted/Completed
+  WS --> CLI: ToolStarted/Completed/Failed
+  WS --> CLI: ApprovalRequired
+  User -> CLI: approve/reject/steer
+  CLI -> WS: ApprovalResponse
+end
+WS --> CLI: SessionCompleted/Failed
+@enduml