feat: add SMS (Telnyx) platform adapter

Implement SMS as a first-class messaging platform following
ADDING_A_PLATFORM.md checklist. All 16 integration points covered:

- gateway/platforms/sms.py: Core adapter with aiohttp webhook server,
  Telnyx REST API send, markdown stripping, 1600-char chunking,
  echo loop prevention, multi-number reply-from tracking
- gateway/config.py: Platform.SMS enum + env override block
- gateway/run.py: Adapter factory + auth maps (SMS_ALLOWED_USERS,
  SMS_ALLOW_ALL_USERS)
- toolsets.py: hermes-sms toolset + included in hermes-gateway
- cron/scheduler.py: SMS in platform_map for cron delivery
- tools/send_message_tool.py: SMS routing + _send_sms() standalone sender
- tools/cronjob_tools.py: 'sms' in deliver description
- gateway/channel_directory.py: SMS in session-based discovery
- agent/prompt_builder.py: SMS platform hint (plain text, concise)
- hermes_cli/status.py: SMS in platforms status display
- hermes_cli/gateway.py: SMS in setup wizard with Telnyx instructions
- pyproject.toml: sms optional dependency group (aiohttp>=3.9.0)
- tests/gateway/test_sms.py: Unit tests for config, format, truncate,
  echo prevention, requirements, toolset integration

Co-authored-by: sunsakis <teo@sunsakis.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

toolsets.py

@@ -292,10 +292,16 @@ TOOLSETS = {
         "includes": []
     },
 
+    "hermes-sms": {
+        "description": "SMS bot toolset - interact with Hermes via SMS (Telnyx)",
+        "tools": _HERMES_CORE_TOOLS,
+        "includes": []
+    },
+
     "hermes-gateway": {
         "description": "Gateway toolset - union of all messaging platform tools",
         "tools": [],
-        "includes": ["hermes-telegram", "hermes-discord", "hermes-whatsapp", "hermes-slack", "hermes-signal", "hermes-homeassistant", "hermes-email"]
+        "includes": ["hermes-telegram", "hermes-discord", "hermes-whatsapp", "hermes-slack", "hermes-signal", "hermes-homeassistant", "hermes-email", "hermes-sms"]
     }
 }