Add README.md and make the template workflow explicit in CLAUDE.md

README covers the copy-clone-rename-build flow and the simple cargo/nix
run commands. CLAUDE.md now states the intended workflow up front
(rename script, then build whatever the user actually wants) instead
of only implying it via the rename-script section.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018ALEXkc7pTro7tF1WcUuKb

CLAUDE.md

@@ -8,7 +8,13 @@ A minimal Rust project template: a `clap`-based CLI (`src/main.rs`) backed by a
 (`src/lib.rs`), with unit tests, an integration test, and a `criterion` benchmark already wired
 up. It also carries a full Nix flake (crane + fenix) so the same build/test/lint pipeline runs
 identically with plain `cargo` or with `nix`. The intent is to eventually turn this into a `nix
-flake init` template — see `scripts/rename-project.sh`.
+flake init` template.
+
+**Workflow for someone starting a new project from this template:** copy/clone the repo, run
+`scripts/rename-project.sh <your_snake_case_name>` to replace the `rust_template` placeholder
+everywhere, `mv` the directory itself (the script prints the exact command), confirm with
+`nix flake check` (or `cargo test`), then build whatever you actually came here to build —
+replace `greet` in `src/lib.rs`, extend the CLI in `src/main.rs`, add real tests/benches as you go.
 
 ## Two ways to work in this repo