Mark project as unmaintained & update Home Assistant Rationale section (#413)

Home assistant's bluetooth integration now accesses BlueZ via D-Bus
directly, and ESPHome bluetooth proxies offer a hardware-based
alternative to local bluetooth access — eliminating the reasons
switchbot-mqtt used to be preferable to the official SwitchBot
integration for home-assistant-only setups.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

AGENTS.md

@@ -5,6 +5,8 @@
 - Attribution line: `Co-Authored-By: Claude <model name> <noreply@anthropic.com>` — always include the model name,
   e.g. `Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>`
 - Do **not** include a `Claude-Session:` line — the session URL is private.
+- Explain **why**, not what — don't restate in prose what's already obvious from `git diff` of
+  the commit (e.g. "add a notice to the README", "update section X").
 
 ## CHANGELOG
 

README.md

@@ -13,6 +13,13 @@ Compatible with [Home Assistant](https://www.home-assistant.io/)'s
 [MQTT Switch](https://www.home-assistant.io/integrations/switch.mqtt/)
 and [MQTT Cover](https://www.home-assistant.io/integrations/cover.mqtt/) platform.
 
+**This project is unmaintained.**
+Home assistant's [bluetooth integration](https://www.home-assistant.io/integrations/bluetooth/)
+now accesses BlueZ via D-Bus directly,
+and [ESPHome bluetooth proxies](https://esphome.io/components/bluetooth_proxy/) offer a
+hardware-based alternative — removing the reasons for using `switchbot-mqtt` alongside home
+assistant explained in section "[Rationale](#rationale)".
+
 ## Setup
 
 ```sh
@@ -129,6 +136,15 @@ runs as `root`.
 This imposes an unnecessary security risk, especially when disabling user namespace remapping
 (`--userns host`).
 
+Nowadays, home assistant's [bluetooth integration](https://www.home-assistant.io/integrations/bluetooth/)
+accesses BlueZ via its D-Bus socket instead of requiring access to the host's network stack,
+and an [ESP32 device running ESPHome](https://esphome.io/components/bluetooth_proxy/)
+can act as a bluetooth proxy without requiring any bluetooth access on the host running home assistant —
+rendering the rationale above obsolete.
+If you're using `switchbot-mqtt` solely as a bridge to home assistant,
+without any other direct MQTT interaction,
+`switchbot-mqtt` has become entirely unnecessary in favor of the official integration.
+
 ### Setup
 
 ```yaml