fix(client): resolve all gdlint warnings — zero warnings policy

Fix 354 gdlint warnings across 65 files: 194 class-definitions-order
(reorder declarations), 138 max-line-length (split long lines),
22 code issues (unused args, no-else-return, naming). Update .gdlintrc
to exclude addons/ and raise max-public-methods for test files.
No logic changes — declaration order, whitespace, and naming only.

Ticket: #783

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/ui/loading_screen.gd

@@ -40,5 +40,5 @@ func show_loading() -> void:
 
 
 ## Hide the loading overlay. success=false is reserved for future failure-state UI.
-func hide_loading(success: bool = true) -> void:
+func hide_loading(_success: bool = true) -> void:
 	visible = false