feat: Add charmbracelet TUI for gt feed (gt-u7dxq)

- Add bubbletea and bubbles dependencies
- Create internal/tui/feed package with:
  - model.go: Main bubbletea model with agent tree and event stream
  - view.go: Rendering logic with lipgloss styling
  - keys.go: Vim-style key bindings (j/k, tab, /, q)
  - styles.go: Color palette and component styles
  - events.go: Event source from bd activity
- Update gt feed to use TUI by default (--plain for text mode)
- TUI features: agent tree by role, event stream, keyboard nav

Closes gt-be0as, gt-lexye, gt-1uhmj

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/tui/feed/keys.go

@@ -0,0 +1,127 @@
+package feed
+
+import "github.com/charmbracelet/bubbles/key"
+
+// KeyMap defines the key bindings for the feed TUI.
+type KeyMap struct {
+	// Navigation
+	Up       key.Binding
+	Down     key.Binding
+	PageUp   key.Binding
+	PageDown key.Binding
+	Top      key.Binding
+	Bottom   key.Binding
+
+	// Panel switching
+	Tab       key.Binding
+	ShiftTab  key.Binding
+	FocusTree key.Binding
+	FocusFeed key.Binding
+
+	// Actions
+	Enter   key.Binding
+	Expand  key.Binding
+	Refresh key.Binding
+
+	// Search/Filter
+	Search      key.Binding
+	Filter      key.Binding
+	ClearFilter key.Binding
+
+	// General
+	Help key.Binding
+	Quit key.Binding
+}
+
+// DefaultKeyMap returns the default key bindings.
+func DefaultKeyMap() KeyMap {
+	return KeyMap{
+		Up: key.NewBinding(
+			key.WithKeys("up", "k"),
+			key.WithHelp("↑/k", "up"),
+		),
+		Down: key.NewBinding(
+			key.WithKeys("down", "j"),
+			key.WithHelp("↓/j", "down"),
+		),
+		PageUp: key.NewBinding(
+			key.WithKeys("pgup", "ctrl+u"),
+			key.WithHelp("pgup", "page up"),
+		),
+		PageDown: key.NewBinding(
+			key.WithKeys("pgdown", "ctrl+d"),
+			key.WithHelp("pgdn", "page down"),
+		),
+		Top: key.NewBinding(
+			key.WithKeys("home", "g"),
+			key.WithHelp("g", "top"),
+		),
+		Bottom: key.NewBinding(
+			key.WithKeys("end", "G"),
+			key.WithHelp("G", "bottom"),
+		),
+		Tab: key.NewBinding(
+			key.WithKeys("tab"),
+			key.WithHelp("tab", "switch panel"),
+		),
+		ShiftTab: key.NewBinding(
+			key.WithKeys("shift+tab"),
+			key.WithHelp("S-tab", "prev panel"),
+		),
+		FocusTree: key.NewBinding(
+			key.WithKeys("1"),
+			key.WithHelp("1", "agent tree"),
+		),
+		FocusFeed: key.NewBinding(
+			key.WithKeys("2"),
+			key.WithHelp("2", "event feed"),
+		),
+		Enter: key.NewBinding(
+			key.WithKeys("enter"),
+			key.WithHelp("enter", "expand/details"),
+		),
+		Expand: key.NewBinding(
+			key.WithKeys("o", "l"),
+			key.WithHelp("o", "toggle expand"),
+		),
+		Refresh: key.NewBinding(
+			key.WithKeys("r"),
+			key.WithHelp("r", "refresh"),
+		),
+		Search: key.NewBinding(
+			key.WithKeys("/"),
+			key.WithHelp("/", "search"),
+		),
+		Filter: key.NewBinding(
+			key.WithKeys("f"),
+			key.WithHelp("f", "filter"),
+		),
+		ClearFilter: key.NewBinding(
+			key.WithKeys("esc"),
+			key.WithHelp("esc", "clear"),
+		),
+		Help: key.NewBinding(
+			key.WithKeys("?"),
+			key.WithHelp("?", "help"),
+		),
+		Quit: key.NewBinding(
+			key.WithKeys("q", "ctrl+c"),
+			key.WithHelp("q", "quit"),
+		),
+	}
+}
+
+// ShortHelp returns key bindings for the short help view.
+func (k KeyMap) ShortHelp() []key.Binding {
+	return []key.Binding{k.Up, k.Down, k.Tab, k.Search, k.Filter, k.Quit, k.Help}
+}
+
+// FullHelp returns key bindings for the full help view.
+func (k KeyMap) FullHelp() [][]key.Binding {
+	return [][]key.Binding{
+		{k.Up, k.Down, k.PageUp, k.PageDown, k.Top, k.Bottom},
+		{k.Tab, k.FocusTree, k.FocusFeed, k.Enter, k.Expand},
+		{k.Search, k.Filter, k.ClearFilter, k.Refresh},
+		{k.Help, k.Quit},
+	}
+}