feat(whatsapp): add slash command handling and text feedback

[reski-rukmantiyo]

Summary

• Add WhatsApp slash commands: /reset, /stop, /stopall, /menu
• Commands are intercepted before the normal message pipeline in inbound.go
• New commands.go handles routing and publishes appropriate InboundMessage events via the bus
• New sendText() helper in outbound.go for direct plain-text replies (used for /menu and /reset confirmation)
• /stop and /stopall delegate feedback to the consumer after cancel result is known

Files changed

• internal/channels/whatsapp/commands.go (new) — command handler with menu help text
• internal/channels/whatsapp/inbound.go — command interception before media/pipeline processing
• internal/channels/whatsapp/outbound.go — sendText() helper for direct text delivery

Test plan

• Send /menu via WhatsApp and verify help text is returned
• Send /reset and confirm conversation history is cleared with confirmation message
• Send /stop during an active task and verify task cancellation
• Send /stopall with multiple active tasks and verify all are cancelled
• Send /unknown and verify it passes through to the normal agent pipeline (not intercepted)
• Send a regular message (no /) and verify it reaches the agent normally

🤖 Generated with Claude Code