[codex] Make Pro guidance metadata-only

[danieliser]

Summary

Make the v2 Extension Framework metadata-only for Legacy → Pro guidance. Popup Maker Core becomes the sole renderer and decision-maker.

Why

Framework-owned offers cannot reach sites whose expired legacy extensions never receive another update. Core has WordPress.org reach and now ships a bundled compatibility catalog for those installations.

What changed

• Remove the ProUpsell controller and all framework-owned notice, plugin-row, script, and notification-panel rendering.
• Remove the framework decision logic that enabled or suppressed those offers.
• Add optional local pro_feature metadata registration through Core's catalog filter.
• Support feature name, priority, historical basenames, license shortnames, classes, and constants.
• Preserve Core's bundled identifiers when metadata enhances an existing record.
• Ignore the old pro_upsell configuration in the new framework release.
• Bump the package to 1.1.0 and document the ownership boundary and metadata format.

The framework makes no remote calls, fetches no offer content or prices, emits no telemetry, and renders no Legacy → Pro UI.

Validation

• PHP syntax: passed
• PHPCS: passed for src/Plugin/Core.php
• Composer validation: structurally valid; strict mode retains the repository's existing warning about declaring a package version
• git diff --check: passed
• This repository does not currently include a formal test suite

Coordinated changes

• [codex] Move legacy extension guidance into Core Popup-Maker#1362 supplies the bundled local catalog and sole notification renderer.
• PopupMaker/Terms-Conditions#12 disables the old renderer for framework 1.0.6 compatibility and registers optional metadata.