README.md: show uv install instructions and fix log.py and __init__.py

Signed-off-by: Ricardo Pardini <ricardo@pardini.net>

Author: rpardini

README.md

@@ -36,6 +36,9 @@ The build has four stages:
 **Prerequisites:** `uv` (Python), Docker.
 
 ```bash
+# Install Astral's `uv` if you don't have it: https://docs.astral.sh/uv/getting-started/installation/
+curl -LsSf https://astral.sh/uv/install.sh | sh # then re-log in
+
 # Build with defaults (amd64, kernel 6.18.16)
 uv run ./build.py --help
 
@@ -176,7 +179,7 @@ Each stage can be executed in one of three modes:
 .
 ├── build.py                    # Main build entry point (Python >= 3.13; use `uv run build.py`)
 ├── captain/                    # Build system package (stdlib only)
-│   ├── __init__.py
+│   ├── __init__.py             # Package init incl logging
 │   ├── cli.py                  # CLI subcommands (argparse)
 │   ├── config.py               # Configuration from environment
 │   ├── docker.py               # Docker builder management
@@ -188,7 +191,6 @@ Each stage can be executed in one of three modes:
 │   ├── skopeo.py               # skopeo CLI wrapper (inspect/copy/export)
 │   ├── iso.py                  # ISO image assembly
 │   ├── qemu.py                 # QEMU boot testing
-│   ├── log.py                  # Colored logging
 │   └── util.py                 # Shared helpers & arch mapping
 ├── Dockerfile                  # Builder container definition
 ├── Dockerfile.release          # Lightweight container for OCI release ops