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.

infrastructure/workflow/AGENTS.md

@@ -0,0 +1,31 @@
+# infrastructure/workflow/
+
+## Purpose
+
+Workflow and prompt loading adapters. Parses TOML workflow definitions into `core:transitions` execution plans (`TomlWorkflowLoader`, `ExecutionPlanCompiler`), loads prompt files from the filesystem (`FileSystemPromptLoader`), and validates plan structure (`PlanLinter`).
+
+## Ownership
+
+Adapter for `core:transitions` and `core:inference` workflow interfaces. Depends on `core:transitions`, `core:inference`, `core:events`, `core:artifacts`. Uses Jackson for TOML parsing.
+
+## Local Contracts
+
+- `WorkflowLoader` (implemented by `TomlWorkflowLoader`) is the interface for reading workflow definitions; implementations must not embed domain logic beyond parsing and structural validation.
+- `PromptLoader` (implemented by `FileSystemPromptLoader`) reads prompt text from disk; filesystem reads are environment observations — callers must record the loaded content as events if replay must reproduce the exact prompt (invariant #9).
+- `ExecutionPlanCompiler` converts the parsed `ExecutionPlanModel` into a runnable plan for `core:transitions`; compilation is deterministic given the same input model.
+- `PlanLinter` enforces structural rules (e.g. unreachable stages are rejected); linting failures throw `WorkflowValidationException`.
+- `PlanDerivedManifest` exposes the write manifest derived from a plan.
+
+## Work Guidance
+
+Standard adapter rules apply (see parent `AGENTS.md`). Filesystem I/O in `withContext(Dispatchers.IO)`. TOML parsing errors must be surfaced as `WorkflowValidationException`, not raw Jackson exceptions.
+
+## Verification
+
+```
+./gradlew :infrastructure:workflow:test --rerun-tasks
+```
+
+## Child DOX Index
+
+No child AGENTS.md (leaf module).