docs: add v3.1.0 changelog entry

CHANGELOG.md

@@ -5,6 +5,22 @@ All notable changes to Hermes Relay will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [3.1.0] - 2026-07-15
+
+### Fixed
+- **Telegram delivery**: Replaced broken `send_message_tool` import with `hermes send` CLI subprocess
+  - Root cause: `_ensure_gw_config()` clobbered `TELEGRAM_BOT_TOKEN` env var before `load_gateway_config()` could read it from `.env`
+  - Fix: `subprocess.run(['hermes', 'send', '--to', 'telegram', '--quiet', text])` — robust, no import hacks
+  - Token must be in `~/.hermes/.env` (not masked `***`); systemd drop-in as backup
+
+### Removed
+- `CircuitBreaker` class and `_tg_circuit_breaker` instance (unused after Telegram delivery refactor)
+- `_ensure_gw_config()` function and associated globals `_gw_config_loaded`, `_gw_config`
+- `tenacity` import (no longer needed)
+
+### Changed
+- Docstring: v3 -> v3.1, fixed Unicode characters
+
 ## [3.0.0] - 2026-06-16
 
 ### Added