refactor: organise source files by ownership

Separate host-independent helpers under common/core and colocate feature
support code with its owners. Update imports, tests, and source-layout
guidance while preserving runtime behaviour.

src/features/ConfigSync/CmdConfigSync.command.unit.spec.ts

@@ -47,7 +47,7 @@ vi.mock("@/common/events.ts", () => ({
 vi.mock("@/common/translation", () => ({
     $msg: vi.fn((message: string) => message),
 }));
-vi.mock("@/common/obsidianCommunityPlugins.ts", () => ({
+vi.mock("@/features/HiddenFileCommon/obsidianCommunityPlugins.ts", () => ({
     getObsidianCommunityPluginManager: vi.fn(),
 }));