docs(locale): clarify full-rollout note on the en fallback default

The Consequences bullet named the zh copy surface the 'zh default', which
could be read as the product's opening locale. It covers component-copy
coverage only; the opening/fallback locale (browser naming no shipped
language, or a non-browser run) is en since FALLBACK_LOCALE moved. State that
explicitly and cross-link the browser-derived-initial-locale note, in both
languages, and re-record the .i18n.yaml pairing.

.agents/notes/implemented/architecture/2026-07-30-client-locale-full-rollout.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/architecture/2026-07-30-client-locale-full-rollout.md
-2026-07-30-client-locale-full-rollout.md: c6c5a8f2faffd3e03462eaad159ae94c53c735ce
-2026-07-30-client-locale-full-rollout.zh.md: 8d6220784104944f5d07b533e4f107ceffdfcfea
+2026-07-30-client-locale-full-rollout.md: 6701aefa451786d3ca6ac27d7214824a6d903bab
+2026-07-30-client-locale-full-rollout.zh.md: 0c05ec9699700d88d786bc661f7013f2ed09ebb2

.agents/notes/implemented/architecture/2026-07-30-client-locale-full-rollout.md

@@ -42,4 +42,4 @@ The "apply layer subscribes to `locale/change` and re-registers for fresh labels
 - A language switch refreshes the whole UI instantly with zero re-registration; adopting a new package is three steps (dictionary + declare-merge + `locale: NS`), no hand-written glue.
 - Cost: list-label consumers must know `resolveSlotLabel` (a raw `options.label` read can now hold a function); the `SlotLabel` type catches most misuse statically.
 - ui-primitives' Chinese defaults still render Chinese under the English locale **until a consumer passes labels** — the unmigrated JsonTree consumer (ui-trajectory) showing its English defaults happens to match that package's all-English status quo.
-- Pinning e2e to English means the zh default is covered mainly by package-level component specs and the settings language-switch scenario; browser e2e no longer asserts zh copy.
+- Pinning e2e to English means the zh copy surface is covered mainly by package-level component specs and the settings language-switch scenario; browser e2e no longer asserts zh copy. The opening/fallback locale (a browser naming no shipped language, or a non-browser run) is `en`, not zh — see [browser-derived initial locale](../feature/2026-07-31-browser-derived-initial-locale.md).

.agents/notes/implemented/architecture/2026-07-30-client-locale-full-rollout.zh.md

@@ -42,4 +42,4 @@ typed locale 标准席位（`locale:` 注册声明 → 框架注入强类型 `t`
 - 语言切换全 UI 即时刷新且零重注册；新包接入 = 字典 + declare-merge + `locale: NS` 三步，无手写胶水。
 - 代价：list label 的消费方必须知道 `resolveSlotLabel`（裸读 `options.label` 现在可能拿到函数）；类型上 `SlotLabel` 已挡住多数误用。
 - ui-primitives 的中文默认值在英文语言下依旧是中文，**直到消费方传入 labels**——未迁移的 JsonTree 消费方（ui-trajectory）显示其英文默认值，恰好符合其整包英文现状。
-- e2e 英文钉死意味着 zh 默认态主要靠包级组件测试与 settings 语言切换用例覆盖，浏览器 e2e 不再验证 zh 文案。
+- e2e 英文钉死意味着 zh 文案面主要靠包级组件测试与 settings 语言切换用例覆盖，浏览器 e2e 不再验证 zh 文案。开场/回落 locale（声明了本应用都不支持语言的浏览器，或非浏览器运行）是 `en` 而非 `zh`，见 [browser-derived initial locale](../feature/2026-07-31-browser-derived-initial-locale.md)。