mcpp-index

Use when adding a new third-party library/package to the mcpp-index repo — writing a pkgs/*/*.lua descriptor, setting up a GitCode CN mirror via gtc, adding a minimal example, and opening a green PR. Covers the four package shapes (C-source compat / header-only / C++23 module / external Form-A module repo), the GLOBAL+CN mirror table, lint rules, the feature (sources-only) gate, and local + CI verification.