feat(settings): configurable selection marker, default off

Adds a Selection Marker toggle under Settings → Preferences that
controls the ❯ cursor glyph on the focused row of every list.
Default off; rows keep a leading space for alignment either way.
Every list pane (tab strip, feed, my shows, discover, search,
settings, whitelist editor) reads the glyph through the shared
useSelectionMarker hook.

Also aligns the lead column across panes: page list rows drop
their extra box paddingLeft so labels start at the same column
as the tab strip (2 cells without nerd icons, 4 with), keeping
episode sub-rows aligned to the title.

src/pages/Settings/PreferencesPanel.tsx

@@ -20,6 +20,7 @@ import { useFeedStore } from "@/stores/feed";
 import { useTheme } from "@/context/ThemeContext";
 import { useInputFocusNav } from "@/hooks/useInputFocusNav";
 import { useScrollIntoView } from "@/hooks/useScrollIntoView";
+import { useSelectionMarker } from "@/hooks/useSelectionMarker";
 import {
 	NavMode,
 	useNavigation,
@@ -88,6 +89,18 @@ export function usePreferencesItems(): SettingItem[] {
 					transparentBackground: !settings().transparentBackground,
 				}),
 		},
+		{
+			id: "showSelectionMarker",
+			label: "Selection Marker",
+			kind: "toggle",
+			display: () => (settings().showSelectionMarker ? "On" : "Off"),
+			help: () =>
+				`Show the ❯ marker on the focused row of every list (tabs, shows, episodes, results).\nType: toggle\nDefault: off\nCurrent: ${settings().showSelectionMarker ? "On" : "Off"}\nSpace/Enter to toggle.`,
+			toggle: () =>
+				app.updateSettings({
+					showSelectionMarker: !settings().showSelectionMarker,
+				}),
+		},
 		{
 			id: "fontSize",
 			label: "Font Size",
@@ -427,6 +440,7 @@ function WhitelistEditor() {
 					const focused = () =>
 						!nav.inputFocused() && index() === wlCursorClamped();
 					const ref = useScrollIntoView(focused);
+					const marker = useSelectionMarker();
 					const bg = () => (focused() ? theme.primary : undefined);
 					const fg = () => (focused() ? theme.surface : theme.text);
 					return (
@@ -434,7 +448,6 @@ function WhitelistEditor() {
 							ref={ref}
 							flexDirection="row"
 							gap={1}
-							paddingLeft={1}
 							paddingRight={1}
 							backgroundColor={bg()}
 							onMouseDown={() => {
@@ -445,7 +458,7 @@ function WhitelistEditor() {
 								wlToggle(feed.id);
 							}}
 						>
-							<text fg={fg()}>{focused() ? "❯" : " "}</text>
+							<text fg={fg()}>{focused() ? marker() : " "}</text>
 							<text fg={fg()}>{inList(feed.id) ? "●" : "○"}</text>
 							<text fg={fg()}>
 								{feed.customName || feed.podcast.title}