docs(dox): build out the DOX AGENTS.md hierarchy

Root Child DOX Index assembled, plus a per-module AGENTS.md across the tree
(core/*, infrastructure/*, apps/*, testing/*, and docs/examples/frontend/etc),
each following the DOX section shape: Purpose, Ownership, Local Contracts,
Work Guidance, Verification, Child DOX Index.

testing/AGENTS.md

@@ -0,0 +1,40 @@
+# testing/
+
+## Purpose
+
+Dedicated test submodules for the correx kernel. Tests here are NOT co-located with production code — each submodule targets a specific verification concern (approval gates, projection correctness, replay determinism, cross-module contracts, integration flows, etc.).
+
+## Ownership
+
+All test submodules in this subtree. Production source is in `core/` and `infrastructure/`; nothing here is deployed.
+
+## Local Contracts
+
+- Tests must not assert on persisted State — only on event-derived state rebuilt by projectors/reducers.
+- No test submodule may import a sibling `testing/*` module except `testing:fixtures`, `testing:kernel`, and `testing:contracts` (shared helpers only).
+- `./gradlew check` applies detekt with `ignoreFailures = false` across all submodules.
+
+## Work Guidance
+
+- Always run tests with `--rerun-tasks` to bypass Gradle cache: `./gradlew :testing:<module>:test --rerun-tasks`
+- Suspend functions in tests use `runBlocking { ... }` — no test coroutine framework needed.
+- Detekt `maxIssues: 120` — do not introduce new rule violations.
+- New `EventPayload` subclass used in tests? Register it in `core/events/.../serialization/Serialization.kt` or deserialization silently fails.
+
+## Verification
+
+```
+./gradlew check   # all submodules: test + detekt + koverVerify
+```
+
+## Child DOX Index
+
+- `testing/approvals` — approval gate logic: grant semantics, security, trigger rules, tier immutability, fuzz
+- `testing/contracts` — cross-module interface contracts and reusable contract test fixtures (projection, replay, inference)
+- `testing/deterministic` — determinism checks: router, session replay, context compression, prompt rendering, validation pipeline
+- `testing/fixtures` — shared test data library: mock implementations, fixture builders, deterministic harness (not a test runner)
+- `testing/integration` — end-to-end flows: orchestrator, tool-call gate, freestyle approval, clarification loop, steering, rehydration
+- `testing/kernel` — core:kernel internals: retry coordinator, approval-before-emit ordering, replay inference provider, context feedback
+- `testing/projections` — reducer and projector correctness for sessions, context, inference, artifacts, router, and journal
+- `testing/replay` — replay determinism: session, approval, validation, transition, decision journal, and repo-knowledge replays
+- `testing/transitions` — FSM/workflow graph: transition resolver, event serialization, fuzz coverage