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-persistence.adoc

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+= infra-persistence
+
+== purpose
+
+Provides concrete `EventStore` implementations for persisting and replaying the event log. Supports in-memory storage (for testing and ephemeral sessions) and SQLite-backed durable storage. Also provides a live artifact repository that subscribes to events and maintains an up-to-date in-memory view of artifact state per session.
+
+== responsibilities
+
+* Implement the `EventStore` interface for both transient and durable storage
+* Enforce duplicate event ID detection and sequence ordering
+* Provide reactive subscriptions via `Flow<StoredEvent>` per session and globally
+* Maintain an artifact state projection that stays current via event subscription
+* Support transactional batch appends for atomic event persistence
+
+== non-responsibilities
+
+* Does not define event serialization — uses `JsonEventSerializer` from `core:events`
+* Does not implement CAS content-addressable storage — that belongs to `infra:artifacts-cas`
+* Does not handle event compaction or retention
+* Does not implement cross-session querying beyond `allSessionIds()`
+
+== key types
+
+=== InMemoryEventStore
+* **kind**: class
+* **purpose**: Thread-safe, in-memory event store backed by `ConcurrentHashMap`. Supports duplicate detection via `seenEventIds` set and session-scoped sequence numbers.
+* **fields**: `streams` (per-session event lists), `sequences` (per-session sequence counters), `globalSeq` (global counter), `seenEventIds` (dedup set)
+
+=== SqliteEventStore
+* **kind**: class
+* **purpose**: Durable event store backed by a SQLite database with WAL mode. Uses JDBC directly. Emits events to reactive flows after append.
+* **fields**: `connection` (JDBC SQLite connection), `jsonSerializer` (serialization bridge), `artifactStore` (used for `flushBefore` coordination)
+
+=== LiveArtifactRepository
+* **kind**: class
+* **purpose**: Subscribes to an `EventStore` per session and maintains an up-to-date in-memory `ConcurrentHashMap` of `ArtifactState` values. Supports lookup by session, stage, and artifact ID.
+* **fields**: `artifactCache` (session → artifactId → state), `stageIndex` (session → artifactId → stageId), `subscriptions` (session → coroutine Job), `projector` (reduces events to state)
+
+=== JDBCHelper
+* **kind**: object
+* **purpose**: Utility providing `Connection.transaction()` inline helper with automatic commit/rollback.
+
+== event flow
+
+*Inbound:*
+* `ArtifactCreatedEvent`, `ArtifactValidatingEvent`, `ArtifactValidatedEvent`, `ArtifactRejectedEvent`, `ArtifactSupersededEvent`, `ArtifactArchivedEvent`, `ArtifactRelationshipAddedEvent` — consumed by `LiveArtifactRepository` to maintain artifact projections
+* `NewEvent` — appended to event stores via `append()` / `appendAll()`
+
+*Outbound:*
+* `StoredEvent` — emitted via `Flow<StoredEvent>` subscriptions after each append
+
+== integration points
+
+* `core:events` — `EventStore`, `StoredEvent`, `NewEvent`, all artifact event payloads, `EventId`, `SessionId`
+* `core:artifacts` — `ArtifactProjector`, `ArtifactReducer`, `ArtifactState`, `ArtifactRepository`
+* `core:artifactstore` — `ArtifactStore` (used by `SqliteEventStore` for flush coordination)
+
+== invariants
+
+* Duplicate `eventId` values are rejected with an error
+* Session sequence numbers are strictly monotonic — violations throw `error()`
+* `InMemoryEventStore.append()` is synchronized per session for thread safety
+* `SqliteEventStore` wraps appends in a JDBC transaction and coordinates with `ArtifactStore.flushBefore()`
+* `LiveArtifactRepository` lazily subscribes on first query and never unsubscribes
+
+== PlantUML diagram
+
+[plantuml, infra-persistence, "png"]
+----
+include::../../diagrams/infra-persistence.puml[]
+----
+
+
+
+
+== known issues
+
+* `SqliteEventStore` holds an open JDBC `Connection` for the lifetime of the application
+* No connection pooling or retry logic for SQLite busy conditions
+
+== open questions
+
+* Should event stores support snapshot-based recovery for long event streams?
+* Should there be a read-replica event store for projections to avoid write-contention?