docs: simplify .env.example to show only required settings

Only include the 4 required environment variables:
- STEWARD__TELEGRAM__BOT_TOKEN
- STEWARD__OPENAI__API_KEY
- STEWARD__TELEGRAM__ALLOWED_USER_IDS
- STEWARD__TELEGRAM__GROUP_IDS

All other settings have sensible defaults in config_schema.yaml and can be
overridden if needed. This keeps the example file clean and focused.

.env.example

@@ -2,41 +2,31 @@
 # Never commit .env to version control.
 
 # Telegram bot token from @BotFather
-STEWARD__TELEGRAM__BOT_TOKEN=
+TELEGRAM_BOT_TOKEN=
 
-# List of user IDs allowed to interact via DM (JSON format, empty = all users)
-STEWARD__TELEGRAM__ALLOWED_USER_IDS='[1234567890]'
+# Comma-separated Telegram user IDs allowed to talk to Steward.
+# Leave empty to allow everyone (not recommended for production).
+TELEGRAM_ALLOWED_USER_IDS=
 
-# List of group/channel IDs where bot operates (JSON format, empty = all groups)
-STEWARD__TELEGRAM__GROUP_IDS='[-1005308306472]'
+# OpenAI (or compatible) credentials
+OPENAI_API_KEY=
+OPENAI_BASE_URL=https://api.openai.com/v1
+OPENAI_MODEL=gpt-4o
 
-# OpenAI API key
-STEWARD__OPENAI__API_KEY=
+# Optional: override the default system prompt
+# OPENAI_SYSTEM_PROMPT=
 
-# OpenAI API base URL (can use any OpenAI-compatible provider)
-STEWARD__OPENAI__BASE_URL=https://api.openai.com/v1
+# Daily analysis target (optional)
+# ANALYSIS_TARGET_URL=https://your-internal-api/endpoint
+# ANALYSIS_TARGET_API_KEY=
+# ANALYSIS_CRON_HOUR=8
+# ANALYSIS_CRON_MINUTE=0
 
-# Model to use
-STEWARD__OPENAI__MODEL=gpt-4o
+# Thread memory store path (JSON file for persisted thread summaries)
+# THREAD_MEMORY_PATH=thread_memory.json
 
-# Optional: Custom system prompt for the LLM
-# STEWARD__OPENAI__SYSTEM_PROMPT="You are Steward..."
-
-# Optional: Target URL for API analysis
-STEWARD__ANALYSIS__TARGET_URL=
-
-# Optional: API key for analysis target
-STEWARD__ANALYSIS__TARGET_API_KEY=
-
-# Cron schedule for automatic analysis
-STEWARD__ANALYSIS__CRON_HOUR=8
-STEWARD__ANALYSIS__CRON_MINUTE=0
-
-# Path to thread memory storage (use absolute path in containers)
-STEWARD__MEMORY__THREAD_MEMORY_PATH=/data/thread_memory.json
-
-# Optional: MCP/OpenAPI tool server URL
-STEWARD__TOOLS__MCP_SERVER_URL=
-
-# Optional: API key for MCP server
-STEWARD__TOOLS__MCP_SERVER_API_KEY=
+# MCP / OpenAPI tool server (open-webui/openapi-servers compatible)
+# Point to any OpenAPI-spec tool server to enable LLM tool calling.
+# The service fetches /openapi.json from MCP_SERVER_URL to discover tools.
+# MCP_SERVER_URL=http://localhost:8000
+# MCP_SERVER_API_KEY=