feat: add Atlas native app UX overhaul

Docs/ADR/ADR-005-Localization-and-App-Language-Preference.md

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+# ADR-005: Localization Framework and App-Language Preference
+
+## Status
+
+Accepted
+
+## Context
+
+Atlas for Mac needed a real multilingual foundation rather than scattered hard-coded English strings. The user requirement was to support Chinese and English first, default to Chinese, and keep the language choice aligned across the app shell, settings, and worker-generated summaries.
+
+## Decision
+
+- Add a package-scoped localization layer with structured resources in `AtlasDomain` so the Swift package graph can share one localization source.
+- Persist the app-language preference in `AtlasSettings` and default it to `zh-Hans`.
+- Inject the selected locale at the app shell while also using the persisted setting to localize worker-generated summaries and settings-derived copy.
+- Keep localized legal copy derived from the selected language rather than treating it as ad hoc free text.
+
+## Consequences
+
+- The app now supports `简体中文` and `English` with Chinese as the default user experience.
+- Settings persistence, protocol payloads, and local workspace state now include the app-language preference.
+- UI automation needs stable identifiers rather than relying only on visible text, because visible labels can now change by language.
+- Future languages can be added by extending the shared localization resources rather than editing each screen in isolation.
+
+## Alternatives Considered
+
+- Use system language only and skip an in-app switch — rejected because the requirement explicitly needed in-app Chinese/English switching.
+- Store language only in app-local UI state — rejected because worker-generated summaries and persisted settings copy would drift from the selected language.
+- Localize each feature independently without a shared resource layer — rejected because it would create duplication and drift across the package graph.