Initial commit: terminal file browser & markdown viewer

A beautiful TUI for browsing files and reading markdown/code:
- Two-pane layout with file tree and content viewer
- Markdown rendering via Glamour
- Syntax highlighting via Chroma
- Auto-detects light/dark terminal theme
- Arrow key navigation, Esc to go back
- Page Up/Down, Home/End for scrolling

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

styles.go

@@ -0,0 +1,32 @@
+package main
+
+import "github.com/charmbracelet/lipgloss"
+
+// Styles - these are initialized by SetTheme() in theme.go
+var (
+	activeBorderStyle   lipgloss.Style
+	inactiveBorderStyle lipgloss.Style
+	directoryStyle      lipgloss.Style
+	fileStyle           lipgloss.Style
+	selectedStyle       lipgloss.Style
+	statusBarStyle      lipgloss.Style
+	statusKeyStyle      lipgloss.Style
+	helpStyle           lipgloss.Style
+	helpTitleStyle      lipgloss.Style
+	helpKeyStyle        lipgloss.Style
+	helpDescStyle       lipgloss.Style
+	titleStyle          lipgloss.Style
+)
+
+// Icon styles - using Unicode geometric shapes for a clean look
+var (
+	iconDir      = "▶"
+	iconDirOpen  = "▼"
+	iconDoc      = "◔"
+	iconCode     = "◇"
+	iconShell    = "▷"
+	iconData     = "◫"
+	iconWeb      = "◈"
+	iconImage    = "◐"
+	iconDefault  = "○"
+)