fix(config): skip skills install without npx

[laipz8200]

Summary

• Check for npx before prompting for or running the Agent Skills installer.
• Mark the Agent Skills setup step as failed and skipped when npx is unavailable, while keeping the saved config usable.
• Align dynamic setup colors so running steps are blue, completed steps are green, and failed steps are red.
• Update English and Chinese docs for the skipped installer behavior.

Impact

Users without Node/npm can still complete confluence-cli config init; only the optional Agent Skills package install is skipped.

Root Cause

The setup flow assumed npx was available and treated installer startup failures as config init failures after the config had already been saved.