feat(templates): add theme template loader via framework TemplateLoader

[aryanjasala]

What this does

Adds a Templates consumer to the theme, mirroring Core\Components — so the
theme can ship PHP template parts that a child theme overrides, resolved through
the framework TemplateLoader. The loader is self-aware: because the theme's own
parts already sit in the (parent) theme, the package layer collapses into the
theme override layer automatically (child theme > parent theme).

Changes

• Add inc/Core/Templates.php — final class Templates extends TemplateLoader implements Shareable; context elementary; points at the theme's
  template-parts/ directory, overridable at child-theme/template-parts/.
• inc/Main.php — register Templates in CLASSES.
• inc/Helpers/Util.php — Util::render_template() (echo) and
  Util::get_template() (string), backed by a shared template_loader() resolved
  via get_shared( Templates::class ) — mirroring Util::component.

How I verified

• php -l clean on changed files.
• Smoke test (framework symlinked): Templates extends TemplateLoader, is
  Shareable with a public no-arg constructor, registered in Main;
  Util::render_template / get_template resolve.

Reviewer notes

• Stacks on the framework TemplateLoader PR. CI/runtime needs that merged to
  main; bump composer.lock to the new main tip once it is.
• theme-elementary is an FSE theme, so this is wiring for any PHP template parts
  the theme (or its child) chooses to ship — no consumer-defined paths; resolution
  and override come from the framework loader.

[Copilot]

Pull request overview

This PR introduces a framework-backed template-part loader to the theme so PHP template parts can be resolved with child-theme overrides (child > parent) via rtCamp\WPFramework\TemplateLoader, plus helper methods to render or retrieve those template parts from PHP.

Changes:

• Added a new Core\Templates loader (TemplateLoader + Shareable) targeting the theme’s template-parts/ directory.
• Registered the new loader in Main::CLASSES so it is bootstrapped with the theme.
• Added Util::render_template() and Util::get_template() helpers backed by the shared Templates instance.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
inc/Main.php	Registers Core\Templates in Main::CLASSES so it loads with the theme bootstrap.
inc/Helpers/Util.php	Adds render_template() / get_template() helper wrappers using the shared Templates loader.
inc/Core/Templates.php	Introduces the new framework TemplateLoader consumer for theme template parts.