fix: stop renaming user-created Telegram topics on bind

[frankjoshua]

Summary

• Removes the automatic topic rename when binding a thread to a window
• Users who create their own named topics in the Telegram supergroup lose their chosen name when ccbot renames it to match the tmux window name
• This preserves user-created topic names while still binding correctly

Test plan

• Create a custom-named topic in the supergroup
• Use /start to bind it to a session
• Verify the topic keeps its original name

🤖 Generated with Claude Code

[six-ddc]

Thanks @frankjoshua for the clean catch — the auto-rename was overriding user-chosen topic names, which is exactly the kind of silent side-effect we want to avoid. Minimal, surgical diff. Merging now. 🙏