feat: add Japanese localization with String Catalog (#819)

* Add i18n infrastructure with String Catalog and Japanese translations

Introduce String Catalog (.xcstrings) for localization support:
- Localizable.xcstrings: 195 UI string entries with en and ja translations
- InfoPlist.xcstrings: Info.plist strings (microphone usage, Finder menu items)
- project.pbxproj: add xcstrings to build phase and ja to knownRegions

* Replace hardcoded UI strings with String(localized:defaultValue:)

Migrate all user-facing strings across 11 source files to use
String(localized:defaultValue:) API (macOS 13+). Each string references
a key in Localizable.xcstrings, with the English text preserved as
defaultValue for fallback.

Files modified:
- KeyboardShortcutSettings: 28 shortcut labels
- SocketControlSettings: mode names and descriptions
- TabManager: placement labels, color names, close dialogs
- BrowserPanel/BrowserPanelView: error pages, context menus, tooltips
- UpdateViewModel/UpdatePopoverView/UpdatePill: update UI states
- NotificationsPage: notification panel labels
- SurfaceSearchOverlay: search bar placeholder and tooltips
- AppDelegate: menus, dialogs, command palette items

* Fix localization gaps from review feedback

Address review comments from CodeRabbit, Greptile, and Cubic Dev AI:
- Use interpolated String(localized:) instead of concatenation for
  version/progress strings in UpdateViewModel
- Localize remaining hardcoded strings in AppDelegate: window labels,
  rename dialog, status menu items, unread notification count
- Localize insecure HTTP alert body in BrowserPanel
- Add 12 new entries to Localizable.xcstrings with Japanese translations

* Fix String(localized:defaultValue:) keys to use StaticString

The localized: parameter requires StaticString when defaultValue: is
used. Move string interpolation from the key to defaultValue only,
and revert maxWidthText to plain strings since they are only used for
layout width calculation.

* Localize remaining UI strings across all source files

Add String(localized:defaultValue:) to all user-facing strings in:
- cmuxApp.swift: settings screen, menus, about panel, dialogs (~180 strings)
- ContentView.swift: command palette, sidebar context menu, dialogs (~200 strings)
- Workspace.swift: rename/move/close tab dialogs, tooltips (~20 strings)
- UpdateTitlebarAccessory.swift: titlebar tooltips, notifications popover (~10 strings)
- TerminalNotificationStore.swift: notification permission dialog (4 strings)
- CmuxWebView.swift: browser context menu items (2 strings)
- AppDelegate.swift: CLI install/uninstall alerts (6 strings)

Add 418 new entries to Localizable.xcstrings with Japanese translations.
Extract sidebar context menu into separate @ViewBuilder to fix Swift
type-checker timeout in large body.
Fix xcstrings format specifiers for interpolated strings (%lld, %@).

Total: 624 localization entries covering the full UI.

* Address review feedback: fix missing localizations and terminology

- Localize javaScriptDialogTitle URL branch in BrowserPanel
- Localize cantReach error message in BrowserPanel
- Localize close other tabs dialog message in TabManager
- Localize workspace accessibility label in ContentView
- Fix unread notification singular/plural (split into two keys)
- Fix insecure connection apostrophe inconsistency (unify to U+2019)
- Rename socketControl.fullOpen.description to socketControl.allowAll.description
- Remove dead code: renameTargetNoun function
- Fix terminology inconsistencies in xcstrings:
  - Unify "Developer Tools" to デベロッパツール
  - Unify "Jump to Latest Unread" phrasing
  - Unify "Flash Focused Panel" terminology
  - Fix dialog.enableNotifications.notNow translation

* fix: address remaining PR 819 review feedback

* fix: use a single localized key for close-other-tabs

* fix: avoid inflection markup in close-other-tabs message

* Address review feedback: localize tooltip, fix subtitle concat, unify keys

- Localize menubar tooltip unread count (hardcoded English -> localized)
- Replace subtitle string concatenation anti-pattern with single localized
  keys containing interpolation placeholders
- Unify workspace fallback key to workspace.displayName.fallback
- Remove unused workspace.defaultName key from xcstrings
- Add Japanese translations for new tooltip and subtitle keys

Sources/SocketControlSettings.swift

@@ -18,30 +18,30 @@ enum SocketControlMode: String, CaseIterable, Identifiable {
     var displayName: String {
         switch self {
         case .off:
-            return "Off"
+            return String(localized: "socketControl.off.name", defaultValue: "Off")
         case .cmuxOnly:
-            return "cmux processes only"
+            return String(localized: "socketControl.cmuxOnly.name", defaultValue: "cmux processes only")
         case .automation:
-            return "Automation mode"
+            return String(localized: "socketControl.automation.name", defaultValue: "Automation mode")
         case .password:
-            return "Password mode"
+            return String(localized: "socketControl.password.name", defaultValue: "Password mode")
         case .allowAll:
-            return "Full open access"
+            return String(localized: "socketControl.allowAll.name", defaultValue: "Full open access")
         }
     }
 
     var description: String {
         switch self {
         case .off:
-            return "Disable the local control socket."
+            return String(localized: "socketControl.off.description", defaultValue: "Disable the local control socket.")
         case .cmuxOnly:
-            return "Only processes started inside cmux terminals can send commands."
+            return String(localized: "socketControl.cmuxOnly.description", defaultValue: "Only processes started inside cmux terminals can send commands.")
         case .automation:
-            return "Allow external local automation clients from this macOS user (no ancestry check)."
+            return String(localized: "socketControl.automation.description", defaultValue: "Allow external local automation clients from this macOS user (no ancestry check).")
         case .password:
-            return "Require socket authentication with a password stored in a local file."
+            return String(localized: "socketControl.password.description", defaultValue: "Require socket authentication with a password stored in a local file.")
         case .allowAll:
-            return "Allow any local process and user to connect with no auth. Unsafe."
+            return String(localized: "socketControl.allowAll.description", defaultValue: "Allow any local process and user to connect with no auth. Unsafe.")
         }
     }
 
@@ -183,7 +183,7 @@ enum SocketControlPasswordStore {
             throw NSError(
                 domain: NSCocoaErrorDomain,
                 code: NSFileNoSuchFileError,
-                userInfo: [NSLocalizedDescriptionKey: "Unable to resolve socket password file path."]
+                userInfo: [NSLocalizedDescriptionKey: String(localized: "socketControl.error.passwordFilePath", defaultValue: "Unable to resolve socket password file path.")]
             )
         }
         let directory = fileURL.deletingLastPathComponent()