Add session detection and running indicator to project launcher

- Add is_session_running() function to detect active tmux sessions
- Update project display to show green "• Running" indicator for active projects
- Fix session detection to use correct session names from project config
- Improve project listing with real-time status information
- Update projects.nix with shortened key names and descriptions

Features:
- Visual feedback for which projects are currently running
- Uses proper tmux session names from project configuration
- Clean green indicator that only appears for running sessions
- Maintains existing project launcher functionality and layout

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

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

config/projects.nix

@@ -41,7 +41,7 @@
       name = "MDShortcut";
       codePath = "/Users/yanlin/Documents/Projects/Material Design Shortcut/MDShortcut-dev";
       paperPath = "/Users/yanlin/Documents/Projects/Material Design Shortcut/MDShortcut-paper";
-      description = "Material Design Shortcut research project";
+      description = "Material design shortcut";
       server = "aicloud";
       remoteDir = "~/MDS";
     };
@@ -53,7 +53,7 @@
       description = "DAKI3 course Demo code";
     };
 
-    diffdismatter = {
+    ddm = {
       template = "research";
       name = "DiffDisMatter";
       codePath = "/Users/yanlin/Documents/Projects/Inverse Design of Disordered Materials/DiffDisMatter-dev";