feat: enhanced UX with per-event messages and file handling

[Fr4nzz]

Summary

• Per-event tool messages: Each tool call (Read, Bash, Grep, etc.) gets its own message with icon, instead of cramming everything into one progress message
• Extended thinking: Show Claude's ThinkingBlocks as 🧠 messages
• Intermediate reasoning: Show visible text between tool calls as 💬 messages
• /cleanup command: Delete tool/thinking messages from the last response on demand
• Progress timer: ⏳ Working... (Xs) updates every 3 seconds, finalizes as ✅ Done (Xs)
• File handling: Rename send_image_to_user → send_file_to_user to accept any file type
• Upload handling: Download files to disk and pass path to Claude (instead of base64)
• Security: Skip file extension whitelist when DISABLE_SECURITY_PATTERNS=true
• HTML fallback: Strip tags in plain text fallback instead of showing raw <b> tags
• _send_formatted_message helper: Consistent HTML-with-fallback across all handlers

Test plan

• Send a text message and verify tool calls appear as individual messages
• Verify 🧠 and 💬 messages appear during processing
• Use /cleanup to delete tool messages after response
• Verify progress shows elapsed time and finalizes as ✅ Done
• Upload a file and verify Claude can read it
• Send an image and verify Claude receives the file path

🤖 Generated with Claude Code