Rename folder to llm-evaluation and link the tutorial in the README

Match the house convention of materials folder = article slug, which the
Trello card gives as "llm-evaluation" (keyphrase "llm evaluation"). Also
add the tutorial link to the README, which was missing, and note the
follow_along/completed split plus how to run in replay and live mode.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: Stephen Gruppetta

build-llm-evaluation-harness-python/README.md

@@ -0,0 +1,26 @@
+# LLM Evaluation in Python: Build an Eval Harness From Scratch
+
+This folder contains the source code for [LLM Evaluation in Python: Build an Eval Harness From Scratch](https://realpython.com/llm-evaluation/).
+
+- `follow_along/` contains the prompts, replay corpus, and setup files that you should start with.
+- `completed/` contains the finished evaluation harness.
+
+## Setup
+
+Move into `follow_along/`, then create your virtual environment and install the dependencies:
+
+```console
+$ uv sync
+```
+
+## Usage
+
+Replay mode is the default and needs no API key, since every command reads recorded generations and judgments from `data/replay/`:
+
+```console
+$ uv run evals.py run --prompt prompts/support_v1.txt
+```
+
+Live mode calls the OpenAI API through the same `ModelClient` protocol. Copy `.env.example` to `.env`, add your key, then pass `--live`.
+
+See the tutorial for the full walkthrough.