refactor(samples): Use concrete TimeWarpTerminal type instead of ITerminal interface

Simplifies sample code by using the concrete terminal type directly,
making the API more discoverable and reducing abstraction overhead
in demonstration code.

🤖 Generated with [opencode](https://opencode.ai)

Co-Authored-By: opencode <noreply@opencode.ai>

Author: StevenTCramer

samples/hyperlink-widget.cs

@@ -6,7 +6,7 @@
 using TimeWarp.Terminal;
 
 // Get a terminal instance
-ITerminal terminal = TimeWarpTerminal.Default;
+TimeWarpTerminal terminal = TimeWarpTerminal.Default;
 
 terminal
   .WriteLine()

samples/panel-widget.cs

@@ -6,7 +6,7 @@
 using TimeWarp.Terminal;
 
 // Get a terminal instance
-ITerminal terminal = TimeWarpTerminal.Default;
+TimeWarpTerminal terminal = TimeWarpTerminal.Default;
 
 terminal
   .WriteLine()

samples/rule-widget.cs

@@ -6,7 +6,7 @@
 using TimeWarp.Terminal;
 
 // Get a terminal instance
-ITerminal terminal = TimeWarpTerminal.Default;
+TimeWarpTerminal terminal = TimeWarpTerminal.Default;
 
 terminal
   .WriteLine()

samples/table-widget.cs

@@ -5,7 +5,7 @@
 using TimeWarp.Terminal;
 
 // Create a terminal for colored output
-ITerminal terminal = new TimeWarpTerminal();
+TimeWarpTerminal terminal = new();
 
 terminal
   .WriteLine("Table Widget Demo")