Add live progress bar to tree search loop

[LouisOwie]

Summary

Adds a live Rich progress bar to the TreeSearch.run() loop, providing real-time
visual feedback during long-running experiments.

Changes

• treesearch/search.py: Wrapped the draft and iteration loops in
  rich.progress.Progress, showing the current step and status
  (e.g. "Iteration 3/5 (debugging)...") directly in the terminal.

Motivation

Long AutoRecLab runs previously had no visual feedback beyond
static log lines. The progress bar communicates at a glance:

• which phase the search is in (drafting vs. iterating)
• current iteration / total
• whether the current node is being debugged or improved

rich was already a project dependency, so no new packages are required.

[eisenbahnhero]

Good work. I completely agree that we should also consider a simple visual output in the future, but perhaps this should be approached in a more comprehensive and asynchronous way.

Before implementing individual steps graphically, I think we should agree on what a front end should look like in the future (desktop tool, website, etc.).