Fix AI skill CLI reference and internal schema paths

Problem

The generated AI-agent skill has two small reference-accuracy problems:

1. Its rendercv new option table documents --create-typst-templates but omits the equally valid --create-markdown-templates option.
2. Every non-classic theme override example preserves the source file's internal comment:

# yaml-language-server: $schema=../../../../../../schema.json

That relative path is only valid inside the RenderCV repository. In the distributable skill it is misleading if copied into a user's file, and it consumes context repeatedly.

Expected behavior

• Document --create-markdown-templates alongside the Typst option.
• Strip repository-local schema comments while generating embedded theme overrides.
• Add regression coverage for both output invariants.