Add launcher project hub and editor project flow

[edisonlee0212]

Summary

• Add a dedicated EvoEngineLauncher/EvoEngineEditor split, retiring EmptyApp and routing project selection/creation through the launcher.
• Add project launch metadata, project-state handling, runtime package template validation, recent-project handling, and automated launcher smoke coverage.
• Add shared ImGui frame/theme helpers, restore LSystem runtime package installability, and document the launcher/editor project metadata flow.

Root Cause / Context

The editor previously had to infer project startup state and carry no-project startup behavior inside the editor itself. Package-backed launcher templates also depended on installed package manifests/DLLs being present, and LSystem was missing a buildable runtime package wrapper, so the launcher marked it unavailable.

Validation

• python Scripts/format_cpp.py --check
• ctest --test-dir out/build/vs2026-x64-tests -C RelWithDebInfo -L launcher --output-on-failure
• ctest --test-dir out/build/vs2026-x64-tests -C RelWithDebInfo -L project --output-on-failure
• ctest --test-dir out/build/vs2026-x64-tests -C RelWithDebInfo -L app --output-on-failure
• python Scripts/install_apps.py --incremental --no-open