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.

frontend/AGENTS.md

@@ -0,0 +1,34 @@
+# frontend/ — AGENTS.md
+
+## Purpose
+
+Early-stage React/TypeScript web UI for the CORREX server. Connects to the server's REST endpoints and WebSocket feed. Placeholder / exploratory state — not production-hardened.
+
+## Ownership
+
+Loosely maintained. Not on the critical path. The canonical operator UI is `apps/tui-go/` (Go/Bubble Tea TUI). This web UI is a secondary surface.
+
+## Local Contracts
+
+- Stack: React 18, TypeScript, `react-scripts` (Create React App).
+- Entry: `src/App.tsx`.
+- Structure: `src/components/`, `src/routes/`, `src/stores/`, `src/lib/`, `src/websocket/`, `src/visualizations/`.
+- Static assets: `static/`.
+- No backend lives here — all data comes from the Ktor server (`apps/server/`).
+- `docs/visual/ref/` is the canonical JS/TS mockup for look-and-feel reference.
+
+## Work Guidance
+
+- Mirror the WS protocol used by `apps/tui-go/` — both clients consume the same server feed.
+- Do not duplicate business logic here; keep components thin and data-driven.
+- Check `docs/visual/ref/` before designing new UI elements.
+
+## Verification
+
+```bash
+cd frontend && npm run build
+```
+
+## Child DOX Index
+
+No child AGENTS.md (leaf directory).