Docs: prerequisites (Android toolchain gap), MQTT broker, cross-project deps

AGENTS.md

@@ -37,6 +37,24 @@ collects usage, and lets Sam override.
   in `kotlin_phone_app_admin`.
 - Chores, quests, or earning screen time. Removed by decision. Do not build it.
 
+## 2a. Prerequisites (verify before Phase 1)
+
+Check these first. Two are missing and will stop you later if ignored.
+
+| Need | Status / note |
+|---|---|
+| **Go toolchain** | Check `go version` on `.13`. Install if missing. |
+| **Docker + compose** | Present on `.13`. Run as user `sam` (in the `docker` group, no sudo). |
+| **MQTT broker** | The **Mosquitto container on `.13:1883`** (running). Use per-device credentials + topic ACLs. Do **not** use Home Assistant's broker on `.30`. |
+| **Android toolchain** | **MISSING on `.13`** — no `java`, `gradle`, `kotlinc`, `adb`, or `sdkmanager`. Needed from **Phase 5**. Decide: install on `.13`, or build the Android client on `.51`. |
+| **Windows test machine** | Needed from **Phase 4** to prove process blocking. |
+| **The phone** | `sams-pixel-8a` is on the tailnet (`100.101.49.17`). ADB wireless can reach it. |
+| **Apprise** | Running on `.35:8210`. |
+| **The Hub** | Live on `.13:8788`. `/ask` is read-only. Contract: `central_ai_llm_master/docs/ask-contract.md`. |
+| **Admin app** | Separate project: `kotlin_phone_app_admin`. It **calls this service**. Do not build it here. |
+
+**Do not start Phase 5 until the Android toolchain question is answered.**
+
 ## 3. Users and roles
 
 | User | Can do |
@@ -59,7 +77,7 @@ collects usage, and lets Sam override.
 | FR-8 | Web dashboard: devices, schedules, blocklists, allowlists, and usage. |
 | FR-9 | Kids' app view: what is blocked now, until when, why, and an alert when a block starts. |
 | FR-10 | Override: a keycode on the device, and remote control from the admin app. |
-| FR-11 | Admin app API: lock, unlock, grant time, and query state. |
+| FR-11 | Admin app API: lock, unlock, grant time, and query state. **Another project consumes this** (`kotlin_phone_app_admin`) — keep the shape small and stable, and version it. |
 | FR-12 | Hub API: `GET /capabilities`, `POST /ask` (read-only), `POST /notify`. |
 | FR-13 | Alerts via Apprise when a limit is hit or a device goes offline too long. |
 | FR-14 | Fail safe: when a device cannot reach the broker, it keeps its last state. |
@@ -137,7 +155,7 @@ The Hub interface is frozen in `central_ai_llm_master/docs/ask-contract.md`.
 | Backend | **Go** |
 | UI | **HTMX** + server-rendered HTML |
 | Database | **SQLite** |
-| Transport | **MQTT** (existing Mosquitto) + HTTP for setup and queries |
+| Transport | **MQTT** on the existing Mosquitto container at `.13:1883` (per-device creds + ACLs) + HTTP for setup and queries |
 | Design | Family Home Lab `tokens.css` |
 | Host | `.13`, Docker |
 | Container | **This project's own** image and compose file. |