feat(ui): auto-filter on typing + refactor item struct with favorites

- Add auto-start filter when typing alphanumeric characters
- Refactor item struct to use explicit station field and isFavorite flag
- Show ★ prefix for favorites in list rendering
- Improve description formatting with bullet separators
- Include URL in FilterValue for better search
- Update help text and add corresponding test

internal/ui/ui.go

@@ -15,12 +15,17 @@ import (
 
 // item wraps a station for the bubbles list.
 type item struct {
-	s radio.Station
+	station    radio.Station
+	isFavorite bool
 }
 
-func (i item) Title() string       { return i.s.Name }
-func (i item) Description() string { return fmt.Sprintf("%s %s %s", i.s.Codec, i.s.Bitrate, truncate(i.s.Url, 50)) }
-func (i item) FilterValue() string { return i.s.Name + " " + i.s.Tags + " " + i.s.Codec }
+func (i item) Title() string { return i.station.Name }
+func (i item) Description() string {
+	return fmt.Sprintf("%s • %s kbps • %s", i.station.Codec, i.station.Bitrate, truncate(i.station.Url, 50))
+}
+func (i item) FilterValue() string {
+	return i.station.Name + " " + i.station.Tags + " " + i.station.Codec + " " + i.station.Url
+}
 
 func truncate(s string, n int) string {
 	if len(s) <= n {
@@ -40,13 +45,16 @@ func (d listDelegate) Render(w io.Writer, m list.Model, index int, listItem list
 	if !ok {
 		return
 	}
-	title := i.s.Name
+	title := i.station.Name
+	if i.isFavorite {
+		title = "★ " + title
+	}
 	if m.Index() == index {
 		title = lipgloss.NewStyle().Bold(true).Render("▶ " + title)
 	} else {
 		title = "  " + title
 	}
-	desc := fmt.Sprintf("   %s • %s kbps • %s", i.s.Codec, i.s.Bitrate, truncate(i.s.Url, 45))
+	desc := fmt.Sprintf("   %s • %s kbps • %s", i.station.Codec, i.station.Bitrate, truncate(i.station.Url, 45))
 	fmt.Fprintf(w, "%s\n%s", title, desc)
 }
 
@@ -70,11 +78,8 @@ func NewApp(initial []radio.Station) *App {
 
 	items := make([]list.Item, len(initial))
 	for i, s := range initial {
-		title := s.Name
-		if favSet[s.Url] {
-			title = "★ " + title
-		}
-		items[i] = item{s: radio.Station{Name: title, Codec: s.Codec, Bitrate: s.Bitrate, Url: s.Url, Tags: s.Tags}}
+		isFav := favSet[s.Url]
+		items[i] = item{station: s, isFavorite: isFav}
 	}
 
 	l := list.New(items, listDelegate{}, 60, 20)
@@ -101,10 +106,26 @@ func (a *App) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 			if i, ok := a.list.SelectedItem().(item); ok {
 				// Placeholder: for now just show what would be played.
 				// Later: switch to playback model + use player.Play
-				a.list.Title = "Would play: " + i.s.Name + " (press q)"
+				a.list.Title = "Would play: " + i.station.Name + " (press q)"
 			}
 			return a, nil
 		}
+
+		// Auto-start filter on first alphanumeric character (better UX than requiring / first)
+		s := msg.String()
+		if len(s) == 1 {
+			r := rune(s[0])
+			if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') {
+				if a.list.FilterState() != list.Filtering {
+					// Simulate pressing the filter key to activate
+					slash := tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{'/'}}
+					a.list, _ = a.list.Update(slash)
+					// Now feed the original key into the active filter
+					a.list, _ = a.list.Update(msg)
+					return a, nil
+				}
+			}
+		}
 	case tea.WindowSizeMsg:
 		a.list.SetSize(msg.Width-4, msg.Height-4)
 	}
@@ -118,7 +139,7 @@ func (a *App) View() string {
 	if a.quitting {
 		return "Thanks for using GoStations!\n"
 	}
-	return "\n" + a.list.View() + "\n\n(enter=play stub • / filter • q quit • --legacy for old UI)\n"
+	return "\n" + a.list.View() + "\n\n(type to filter • enter=play stub • / or letters for filter • q quit • --legacy for old UI)\n"
 }
 
 // Run starts the TUI (alt screen).

internal/ui/ui_test.go

@@ -27,3 +27,27 @@ func TestApp_BasicKeyHandling(t *testing.T) {
 		t.Log("list size not updated (may be ok in test)")
 	}
 }
+
+func TestApp_AutoFilterOnTyping(t *testing.T) {
+	app := NewApp([]radio.Station{
+		{Name: "WFMT 98.7", Url: "http://wfmt", Codec: "MP3", Bitrate: "128", Tags: "chicago,classical"},
+		{Name: "Other Station", Url: "http://other", Codec: "AAC", Bitrate: "64", Tags: "news"},
+	})
+
+	// Simulate typing 'W' (should auto enter filter and filter to WFMT)
+	model, _ := app.Update(tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{'W'}})
+	a := model.(*App)
+
+	// After auto filter start + 'W', the filter value should be "W" and state Filtering or applied
+	fv := a.list.FilterValue()
+	if fv != "W" {
+		t.Errorf("expected filter value 'W' after typing W, got %q", fv)
+	}
+
+	// The visible items should be filtered (at least the WFMT one should match)
+	visible := a.list.VisibleItems()
+	if len(visible) == 0 {
+		t.Error("expected some visible items after filter 'W'")
+	}
+	// Check that 'Other' is not the only one, or better, since fuzzy, 'W' may match others weakly, but at least not empty
+}