Move library and tool implementations into domains

[TrapEmAll]

What changed

• Move the complete external Tool Center implementation into unityscraper.domains.tools, including models, catalog/discovery, command construction, and process execution.
• Move the read-only library query service and GameSummary model into unityscraper.domains.library.
• Keep external_tools.py, tool_catalog.py, and library_service.py as compatibility wrappers for existing users.
• Update desktop and CLI consumers to import the package-owned implementations directly.
• Add ownership regression tests and update the modularization roadmap.

Why

The initial modular foundation exposed package adapters, but several domain modules still imported their real implementations from top-level legacy files. This change reverses that dependency for two cleanly bounded areas, making the domain packages the source of truth while preserving existing imports.

Impact

Behavior and public compatibility imports are unchanged. New development can now build on domain-owned library and Tool Center services without depending on legacy application modules.

Validation

• python tests.py (131 passed)
• python integration_tests.py (31 passed)
• Ruff passed
• Python compilation passed
• Version consistency passed
• git diff --check passed