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/integration/AGENTS.md

@@ -0,0 +1,30 @@
+# testing/integration
+
+## Purpose
+
+End-to-end integration tests that wire multiple core modules together without live LLM or network. Covers: `SessionOrchestrator` full flows, tool-call gate, freestyle approval gate, clarification loop, steering preemption, graph reroute, artifact injection, workspace-scoped tool registry, validation pipeline integration, critique calibration wiring, session rehydration, repo-map reuse, and subagent runner seam.
+
+## Ownership
+
+Tests in this submodule. Production modules exercised: `core:events`, `core:sessions`, `core:transitions`, `core:validation`, `core:approvals`, `core:context`, `core:inference`, `core:kernel`, `core:journal`, `core:risk`, `core:tools`, `core:toolintent`, `core:artifacts`, `core:artifacts-store`, `core:router`, `core:config`, `infrastructure:persistence`, `infrastructure:tools`, `infrastructure:tools:filesystem`, `apps:server`.
+
+## Local Contracts
+
+- Tests use mock inference (`MockInferenceProvider` from `testing:fixtures`) — no live LLM.
+- `apps:server` is imported for Ktor wiring tests only; no external HTTP calls.
+- Two-plane validation (Plane 2 / `core:toolintent`) must be exercised by at least one test here — `ToolCallGateTest` covers this.
+
+## Work Guidance
+
+- Suspend tests use `runBlocking { ... }` or `kotlinx-coroutines-test`.
+- These are the slowest tests; run targeted with `:testing:integration:test --tests "ClassName"` during development.
+
+## Verification
+
+```
+./gradlew :testing:integration:test --rerun-tasks
+```
+
+## Child DOX Index
+
+No child AGENTS.md (leaf module).