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>

keys.go

@@ -0,0 +1,70 @@
+package main
+
+import "github.com/charmbracelet/bubbletea"
+
+// Key represents a key binding
+type Key struct {
+	Keys []string
+	Help string
+}
+
+func (k Key) Matches(msg tea.KeyMsg) bool {
+	for _, key := range k.Keys {
+		if msg.String() == key {
+			return true
+		}
+	}
+	return false
+}
+
+// Keybindings for the application
+var (
+	keyUp = Key{
+		Keys: []string{"up"},
+		Help: "move up",
+	}
+	keyDown = Key{
+		Keys: []string{"down"},
+		Help: "move down",
+	}
+	keyLeft = Key{
+		Keys: []string{"left"},
+		Help: "collapse/parent",
+	}
+	keyRight = Key{
+		Keys: []string{"right"},
+		Help: "expand/open",
+	}
+	keyEnter = Key{
+		Keys: []string{"enter"},
+		Help: "open/toggle",
+	}
+	keyEscape = Key{
+		Keys: []string{"esc"},
+		Help: "back to files",
+	}
+	keyPageDown = Key{
+		Keys: []string{"pgdown"},
+		Help: "page down",
+	}
+	keyPageUp = Key{
+		Keys: []string{"pgup"},
+		Help: "page up",
+	}
+	keyHome = Key{
+		Keys: []string{"home"},
+		Help: "go to top",
+	}
+	keyEnd = Key{
+		Keys: []string{"end"},
+		Help: "go to bottom",
+	}
+	keyHelp = Key{
+		Keys: []string{"?"},
+		Help: "toggle help",
+	}
+	keyQuit = Key{
+		Keys: []string{"q", "ctrl+c"},
+		Help: "quit",
+	}
+)