fix(npm): add npm to cg update methods, normalize repository.url

[khooihzhz]

Summary

• cg update now detects npm installs (executable path under node_modules/@coingecko/cg-) and runs npm install -g @coingecko/cg@latest. Previously it fell through to the script branch and curl-installed a second cg binary to /usr/local/bin/, shadowing the npm copy.
• Reordered detection so npm runs before homebrew: Homebrew-installed Node puts npm globals under /opt/homebrew/lib/node_modules/, which would otherwise match the homebrew rule.
• Added git+ prefix to repository.url in all 7 npm/*/package.json templates. Silences the npm warn publish "repository.url" was normalized to ... warning seen on every release (e.g. run 25838686514).
• Documented npm distribution + cg update method ordering in CLAUDE.md and the npm method override in README.

Test plan

• make test (added TestClassifyInstallPath_Npm covering macOS/Linux/Homebrew-Node/Windows paths; updated TestDetectInstallMethod_ReturnsValidMethod to include npm)
• make lint
• After merge, tag a new release and verify the npm publish step no longer prints repository.url was normalized warnings
• Verify cg update on a node_modules-installed binary runs npm install -g @coingecko/cg@latest instead of install.sh