Split App helpers into editor modules and add toolbar auto-collapse hook

[neptunusRomulus]

Motivation

• Reduce complexity in App.tsx by moving editor/business logic and static metadata into focused feature modules under src/editor so App.tsx remains an orchestrator.
• Make toolbar collapse behavior reusable and testable by extracting it into a hook under src/hooks.
• Improve code organization and enable easier unit testing and maintenance of editor utilities.

Description

• Extracted map spawn helpers into src/editor/mapSpawnUtils.ts and exported computeIntermapTarget, buildSpawnContent, extractSpawnIntermapValue, and STARTING_MAP_INVALID_NAMES.
• Moved object validation into src/editor/objectValidation.ts and exported validateAndSanitizeObject plus related types and spec placeholders.
• Moved item/actor role metadata and rule option lists into src/editor/itemRoles.ts, src/editor/actorRoles.ts, and src/editor/ruleOptions.ts and updated App.tsx imports to consume them.
• Added useToolbarAutoCollapse in src/hooks/useToolbarAutoCollapse.ts, wired the main, bottom, and brush toolbars to use it (with brush toolbar autoCollapse disabled), and cleaned up some unused icon imports in App.tsx.

Testing

• No automated tests were executed for this change.
• Local type/runtime validation was not performed as part of this commit (no test suite run).

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Codex Task