refactor(home): drop the labels for two rows the home page stopped offering

`SplitRight` and `SplitDown` were taken out of `HOME_SHORTCUTS` because
both need a pane and the home page is what a window shows without one —
"advertising two chords that do nothing from the only screen that offers
them", as the comment there puts it, with a test to keep them out.

Their labels stayed. `home_shortcut_label` still had an arm for each, and
`HomeSplitRight`/`HomeSplitDown` were carried in three locale tables to
serve those arms and nothing else.

Nothing could point this out. The single caller iterates
`HOME_SHORTCUTS`, so the arms are unreachable — but `_ => action` makes
the match total, so no compiler warning, and the keys are textually
referenced, so `dead_code` sees them as used. Only reading the caller
does it.

Removing the enum variants is what makes this safe rather than hopeful:
the three locale tables match `L10nKey` exhaustively, so the compiler
named every translation to delete and would have caught a fourth.

src/ui/home.rs

@@ -162,8 +162,6 @@ fn home_shortcut_label(action: &str, closed: Option<&str>) -> String {
         "ReopenClosedTab" => crate::ui::i18n::t(crate::ui::i18n::L10nKey::HomeReopenClosedTab),
         "ToggleSwitcher" => crate::ui::i18n::t(crate::ui::i18n::L10nKey::HomeSwitchWorkspace),
         "TogglePalette" => crate::ui::i18n::t(crate::ui::i18n::L10nKey::HomeCommandPalette),
-        "SplitRight" => crate::ui::i18n::t(crate::ui::i18n::L10nKey::HomeSplitRight),
-        "SplitDown" => crate::ui::i18n::t(crate::ui::i18n::L10nKey::HomeSplitDown),
         "OpenSettings" => crate::ui::i18n::t(crate::ui::i18n::L10nKey::HomeSettings),
         _ => action,
     };

src/ui/i18n/en.rs

@@ -20,8 +20,6 @@ pub fn translate_en(key: L10nKey) -> &'static str {
         L10nKey::HomeReopenClosedTab => "Reopen Closed Tab",
         L10nKey::HomeSwitchWorkspace => "Switch Workspace…",
         L10nKey::HomeCommandPalette => "Command Palette…",
-        L10nKey::HomeSplitRight => "Split Right",
-        L10nKey::HomeSplitDown => "Split Down",
         L10nKey::HomeSettings => "Settings…",
         L10nKey::Reconnect => "Reconnect",
         L10nKey::None => "None.",

src/ui/i18n/ja.rs

@@ -20,8 +20,6 @@ pub fn translate_ja(key: L10nKey) -> Option<&'static str> {
         L10nKey::HomeReopenClosedTab => "閉じたタブをもう一度開く",
         L10nKey::HomeSwitchWorkspace => "ワークスペースを切り替える…",
         L10nKey::HomeCommandPalette => "コマンドパレット…",
-        L10nKey::HomeSplitRight => "右に分割",
-        L10nKey::HomeSplitDown => "下に分割",
         L10nKey::HomeSettings => "設定…",
         L10nKey::Reconnect => "再接続",
         L10nKey::None => "なし",

src/ui/i18n/mod.rs

@@ -98,8 +98,6 @@ l10n_keys! {
     HomeReopenClosedTab,
     HomeSwitchWorkspace,
     HomeCommandPalette,
-    HomeSplitRight,
-    HomeSplitDown,
     HomeSettings,
     Reconnect,
     None,

src/ui/i18n/zh.rs

@@ -20,8 +20,6 @@ pub fn translate_zh(key: L10nKey) -> Option<&'static str> {
         L10nKey::HomeReopenClosedTab => "重新打开已关闭的标签页",
         L10nKey::HomeSwitchWorkspace => "切换工作区…",
         L10nKey::HomeCommandPalette => "命令面板…",
-        L10nKey::HomeSplitRight => "向右分屏",
-        L10nKey::HomeSplitDown => "向下分屏",
         L10nKey::HomeSettings => "设置…",
         L10nKey::Reconnect => "重新连接",
         L10nKey::None => "无。",