LRC-LIB-SMARTCOLL: document message contexts for translators

localization.md explains "<context>|<English>" catalog keys and the one
context today (smart album value); localization-ja.md notes あり / なし.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/localization-ja.md

@@ -24,5 +24,9 @@ LightCraft は日本語・簡体字中国語・英語（English）の表示に
 英語の単複数語尾を日本語で省略する場合、対応する文字列引数は `{:.0}` で空にします。
 `LIGHTCRAFT_LANGUAGE=ja lightcraft-cli snapshot ...` で日本語の画面を描画できます。
 
+スマートアルバムの「はい／いいえ」で答える条件（編集あり、切り抜き済みなど）の値は、文脈付きキー
+`"smart album value|Yes"`・`"smart album value|No"` で「あり／なし」と表示します。共有の
+`"Yes"`・`"No"`（はい／いいえ）は他の画面でそのまま使います（[`localization.md`](localization.md) の文脈の説明を参照）。
+
 表示・フォント・言語の切り替え・設定の保存・コマンドIDの保持は
 `cargo test -p lightcraft-ui-egui i18n::tests` で検証します（グリフの検査は `CRAFT_FONTS_DIR` 指定時のみ実行）。

docs/localization.md

@@ -49,6 +49,14 @@ are in [`localization-zh-hans.md`](localization-zh-hans.md), [`localization-zh-h
 text unchanged when there is no entry; `tr_format!` handles text with runtime values. Both are
 presentation-only: command ids, file names and user-entered metadata are never translated.
 
+A few messages take a **context**, for a word whose shared translation reads wrongly in one place.
+The catalog may then carry `"<context>|<English>"`, which wins there; without it the plain message
+is used, so only the languages that need it add one. Today the one context is `smart album value`:
+the Yes / No of a yes/no rule (Has Edits, Cropped…). Japanese uses it because はい / いいえ answer a
+question rather than describe a photo (`"smart album value|Yes": "あり"`, `"smart album value|No":
+"なし"`); every other language uses its plain Yes / No. A contextual key that names no real value
+fails the i18n tests.
+
 `tr_format!` is generated by `crates/ui-egui/build.rs`: one arm per English message, which formats
 the active language's translation with `format!` (English is the fallback arm). Every catalog's
 format string is therefore checked by Rust against the call site's own arguments: