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/testing/test-projections.adoc

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+= test-projections
+
+== purpose
+
+Unit tests for the event-sourced projection and reducer components. Verifies that each projector correctly rebuilds state from a sequence of events, and that reducers produce the correct state transitions for each event type.
+
+== responsibilities
+
+* Test `DefaultSessionReducer` and `SessionProjector` — session lifecycle state transitions
+* Test `DefaultOrchestrationReducer` and `OrchestrationProjector` — orchestration state transitions
+* Test `InferenceReducer` and `InferenceProjector` — inference state tracking
+* Test `DefaultContextReducer` and `ContextProjector` — context state tracking
+* Test `ArtifactReducer` — artifact metadata state tracking
+* Test `RouterReducer` and `RouterProjector` — router state tracking
+
+== non-responsibilities
+
+* Does not test live event streaming or real-time event processing
+* Does not test the event store write path
+* Does not test the `SessionOrchestrator` or higher-level orchestration logic
+* Does not test application layers
+
+== key types
+
+=== DefaultSessionReducerTest
+* **kind**: JUnit 5 test class
+* **purpose**: Tests `DefaultSessionReducer` with session lifecycle events (start, pause, resume, fail, complete). Verifies status transitions and state field updates.
+
+=== SessionProjectorTest
+* **kind**: JUnit 5 test class
+* **purpose**: Tests `SessionProjector` by feeding sequences of events through the projector and verifying the final `SessionState`.
+
+=== OrchestrationReducerTest
+* **kind**: JUnit 5 test class
+* **purpose**: Tests `DefaultOrchestrationReducer` with orchestration events (stage transitions, approvals, retries). Verifies state machine transitions.
+
+=== OrchestrationProjectorTest
+* **kind**: JUnit 5 test class
+* **purpose**: Tests `OrchestrationProjector` by replaying orchestration event sequences and validating the final `OrchestrationState`.
+
+=== InferenceReducerTest / InferenceProjectorTest
+* **kind**: JUnit 5 test classes
+* **purpose**: Tests inference event reduction and projection — request lifecycle, completion, timeout, and failure.
+
+=== ContextReducerTest / ContextProjectorTest
+* **kind**: JUnit 5 test classes
+* **purpose**: Tests context pack building and compression through the projection pipeline.
+
+=== RouterReducerTest / RouterProjectorTest
+* **kind**: JUnit 5 test classes
+* **purpose**: Tests router state projection — tracks router interaction history and state.
+
+=== ArtifactReducerTest
+* **kind**: JUnit 5 test class
+* **purpose**: Tests artifact metadata reduction from tool execution events.
+
+== event flow
+
+*inbound:* Constructed `StoredEvent` sequences representing the full lifecycle of a session or subsystem.
+
+*outbound:* Assertions on the final projected `*State` object, comparing field-by-field against expected values.
+
+== integration points
+
+* `:core:sessions` — `DefaultSessionReducer`, `SessionProjector`, `SessionState`
+* `:core:kernel` — `DefaultOrchestrationReducer`, `OrchestrationProjector`, `OrchestrationState`
+* `:core:inference` — `InferenceReducer`, `InferenceProjector`, `InferenceState`
+* `:core:context` — `DefaultContextReducer`, `ContextProjector`, context state types
+* `:core:artifacts` — `ArtifactReducer`
+* `:core:router` — `RouterReducer`, `RouterProjector`
+* `:core:events` — `StoredEvent`, all event payload types
+* `:testing:fixtures` — `EventFixtures`
+
+== invariants
+
+* Each projector produces the same final state given the same event sequence, regardless of intermediate projections
+* Reducers only modify state via `state.copy(...)` — no side effects
+* Unknown event types in a reducer return the state unchanged
+
+== PlantUML diagram
+
+[plantuml, test-projections, "png"]
+----
+include::../../diagrams/test-projections.puml[]
+----
+
+
+
+
+== known issues
+
+* Tests may not cover all edge cases (empty event lists, out-of-order events, duplicate events)
+* Event sequences are constructed manually and may not reflect real-world ordering guarantees from the event store
+
+== open questions
+
+* Should projection tests verify behavior with interleaved events from multiple sessions?
+* Should there be property-based tests (e.g., `kotlinx.kotest.properties`) verifying the projector invariants across random event sequences?