fix(search): the All tab's placeholder names what All searches

Files left Search Everywhere's All tab and Actions became Commands, but
its placeholder still offered "files, actions, terminals and hosts" and
did not mention sessions. Name the four scopes it actually covers, in
English, Chinese and Japanese.

src/ui/i18n/en.rs

@@ -161,7 +161,7 @@ pub fn translate_en(key: L10nKey) -> &'static str {
         L10nKey::SearchTabTerminals => "Terminals",
         L10nKey::SearchTabHosts => "Hosts",
         L10nKey::SearchTabSymbols => "Symbols",
-        L10nKey::SearchPlaceholderAll => "Search files, actions, terminals and hosts…",
+        L10nKey::SearchPlaceholderAll => "Search terminals, sessions, hosts and commands…",
         L10nKey::SearchPlaceholderActions => "Search commands…",
         L10nKey::SearchPlaceholderTerminals => "Search open tabs, shells and agents…",
         L10nKey::SearchPlaceholderHosts => "Search hosts, or type user@host to connect…",

src/ui/i18n/ja.rs

@@ -172,7 +172,7 @@ pub fn translate_ja(key: L10nKey) -> Option<&'static str> {
         L10nKey::SearchTabTerminals => "ターミナル",
         L10nKey::SearchTabHosts => "ホスト",
         L10nKey::SearchTabSymbols => "シンボル",
-        L10nKey::SearchPlaceholderAll => "ファイル、アクション、ターミナル、ホストを検索…",
+        L10nKey::SearchPlaceholderAll => "ターミナル、セッション、ホスト、コマンドを検索…",
         L10nKey::SearchPlaceholderActions => "コマンドを検索…",
         L10nKey::SearchPlaceholderTerminals => "開いているタブ、シェル、エージェントを検索…",
         L10nKey::SearchPlaceholderHosts => "ホストを検索、または user@host を入力して接続…",

src/ui/i18n/zh.rs

@@ -142,7 +142,7 @@ pub fn translate_zh(key: L10nKey) -> Option<&'static str> {
         L10nKey::SearchTabTerminals => "终端",
         L10nKey::SearchTabHosts => "主机",
         L10nKey::SearchTabSymbols => "符号",
-        L10nKey::SearchPlaceholderAll => "搜索文件、操作、终端和主机…",
+        L10nKey::SearchPlaceholderAll => "搜索终端、会话、主机和命令…",
         L10nKey::SearchPlaceholderActions => "搜索命令…",
         L10nKey::SearchPlaceholderTerminals => "搜索已打开的标签页、Shell 和 Agent…",
         L10nKey::SearchPlaceholderHosts => "搜索主机，或输入 user@host 连接…",