feat(client): typed locale standard seat in the slot framework

Registrations declare a dictionary namespace (locale: NS) and the renderer
synthesizes a typed t prop for the entry's component from the installed
LocaleFace; the seat binding is re-derived per locale revision, so a language
switch hands out fresh t references and memoized consumers re-render through
ordinary shallow comparison. LocaleNamespaceMap is the declare-merge table
(namespace -> dictionary key union); TranslateNS<'ns'> is the
namespace-addressed translate type (namespace keys plus the shared common
vocabulary), carried by the t seat and by the locale service's typed bind.

LocaleService implements the face (lookup ns -> common -> zh -> key,
revision-carrying snapshots with subscriber isolation) and installs it
through the boot-once slots.installLocale seam, mirroring the renderer
install. The typed register(ns, {zh, en}) overload checks each dictionary
against the namespace's key union and requires every shipped locale, so a
missing or extra key and an unbalanced translation are compile errors.
Dictionary registration bumps the face revision without emitting
locale/change — the event now means exactly 'the active locale switched',
so registration-heavy boot cannot storm event listeners.

packages/client/locale/src/locales/en.ts

@@ -1,2 +1,29 @@
-/** en base dictionary for the common namespace (starter skeleton; texts land with their features). */
-export const en: Record<string, string> = {}
+import type { CommonKey } from './zh.ts'
+
+/** en base dictionary for the common namespace, checked complete against the zh key set. */
+export const en = {
+  'ok': 'OK',
+  'cancel': 'Cancel',
+  'close': 'Close',
+  'copy': 'Copy',
+  'copied': 'Copied',
+  'retry': 'Retry',
+  'loading': 'Loading…',
+  'load.failed': 'Failed to load',
+  'submit': 'Submit',
+  'submitting': 'Submitting…',
+  'next': 'Next',
+  'previous': 'Previous',
+  'skip': 'Skip',
+  'delete': 'Delete',
+  'edit': 'Edit',
+  'save': 'Save',
+  'search': 'Search',
+  'more': 'More',
+  'collapse': 'Collapse',
+  'expand': 'Expand',
+  'back': 'Back',
+  'unknown': 'Unknown',
+  'none': 'None',
+  'truncated': 'Truncated',
+} satisfies Record<CommonKey, string>

packages/client/locale/src/locales/index.ts

@@ -0,0 +1,8 @@
+/**
+ * The common-namespace dictionary pair. zh is the source of truth for the
+ * key set (Chinese-first repo convention); en is checked complete against it
+ * — a missing or extra en key is a compile error.
+ */
+export { zh } from './zh.ts'
+export { en } from './en.ts'
+export type { CommonKey } from './zh.ts'

packages/client/locale/src/locales/settings.ts

@@ -0,0 +1,14 @@
+/** `settings.locale` namespace dictionaries (the Language row's copy). */
+
+/** Simplified Chinese dictionary (the key-set source of truth). */
+export const zh = {
+  'language.title': '语言',
+} satisfies Record<string, string>
+
+/** The settings.locale namespace key union. */
+export type SettingsLocaleKey = keyof typeof zh
+
+/** English dictionary, checked complete against the zh key set. */
+export const en = {
+  'language.title': 'Language',
+} satisfies Record<SettingsLocaleKey, string>

packages/client/locale/src/locales/zh.ts

@@ -1,2 +1,30 @@
-/** zh base dictionary for the common namespace (starter skeleton; texts land with their features). */
-export const zh: Record<string, string> = {}
+/** zh base dictionary for the common namespace: cross-feature standard words. */
+export const zh = {
+  'ok': '确定',
+  'cancel': '取消',
+  'close': '关闭',
+  'copy': '复制',
+  'copied': '复制成功',
+  'retry': '重试',
+  'loading': '加载中…',
+  'load.failed': '加载失败',
+  'submit': '提交',
+  'submitting': '正在提交…',
+  'next': '下一步',
+  'previous': '上一步',
+  'skip': '跳过',
+  'delete': '删除',
+  'edit': '编辑',
+  'save': '保存',
+  'search': '搜索',
+  'more': '更多',
+  'collapse': '收起',
+  'expand': '展开',
+  'back': '返回',
+  'unknown': '未知',
+  'none': '无',
+  'truncated': '已截断',
+} satisfies Record<string, string>
+
+/** The common vocabulary key union (zh is the key-set source of truth). */
+export type CommonKey = keyof typeof zh