docs: clarify uvx vs uv tool install in CLAUDE_CODE_SETUP.md

[vibeyclaw]

Fixes #4499

What changed

The # Try without installing (temporary) comment on uvx amplihack install was misleading — it implies nothing is installed, but uvx amplihack install still runs amplihack's install command and sets up agents/skills in the current project directory.

Changes

• Rewrote the two code comments in the Permanent Setup section to clearly label each as Option 1 / Option 2 with a description of what each does
• Added a > Note block below the code block explaining the real difference: uvx runs it without permanently adding amplihack to PATH, while uv tool install does

Before / After

Before:

# Try without installing (temporary)
uvx amplihack install

# Or install permanently
uv tool install amplihack

After:

# Option 1: Run via uvx (no permanent entry in PATH, but still installs amplihack's
# agents/skills into your project — suitable for trying it out)
uvx amplihack install

# Option 2: Install permanently (adds `amplihack` to your PATH via uv)
uv tool install amplihack

Note: uvx amplihack install does run amplihack's install command... The difference from Option 2 is that the amplihack binary itself is not added to your PATH permanently...