v1.28.0: flatten all service/use-case classes to free functions, delete FileService watcher and dead UpdaterService pass, i18n for sidebar hide-tab, fix freezing status

docs: update all READMEs to v1.27.0, fix plugin example, remove old PluginAPI references

v1.27.0: ponytail shutdown: delete find_project_root/__dataclass_fields__/AsyncRuntime/PluginAPI/FsRepo, extract get_resource_path, clean aggressive_minify/regedits/spinner; fix hello_world plugin import, restore plugins tab visibility

v1.26.2: merge visit methods, delegate PatchService, webbrowser opener, DRY sidebar comboboxes

ponytail: fix PDF filter and diff pairing