Move tools/cli/ to tools/installer/ with major structural cleanup:
- InstallPaths async factory for path resolution and directory creation
- Config value object (frozen) replaces mutable config bag
- ExistingInstall value object replaces stateful Detector class
- OfficialModules + CustomModules + ExternalModuleManager replace monolithic ModuleManager
- install() is prompt-free; all user interaction in ui.js
- Update state returned explicitly instead of mutating customConfig
- Delete dead code: dependency-resolver, _base-ide, IdeConfigManager,
platform-codes helpers, npx wrapper, xml-utils
- Flatten directory structure: custom/handler → custom-handler,
tools/cli/ → tools/installer/, lib/ directories removed
- Update all path references in package.json, tests, CI, and docs
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