Verify enum lookup behavior against realistic JoyButton XML fixture

[deevus]

Parent

Parent PRD: #5

What to build

Add a realistic end-to-end regression fixture modeled on Godot's JoyButton enum. The fixture should verify both lookup spellings, readable markdown/terminal-safe output, value listings, numeric values, descriptions, and compatibility with existing individual enum value lookups. This is a testing hardening slice and should not introduce new behavior beyond validating the completed enum lookup flow.

Acceptance criteria

• A realistic JoyButton-style fixture exercises global enum container generation end-to-end.
• Tests verify JoyButton and @GlobalScope.JoyButton both resolve successfully.
• Tests verify output includes representative JOY_BUTTON_* values, numeric values, and descriptions.
• Tests verify existing enum value lookup compatibility remains intact.
• Tests verify output remains suitable for markdown and terminal rendering paths.
• The regression coverage is behavior-focused and avoids brittle implementation-detail assertions.

Blocked by

• Generate fully-qualified enum container docs #6
• Add short aliases for global enum containers #7