feature/go-rewrite : base Go avec walk GUI

- Rewrite complet en Go : exe unique sans _internal/, sans extraction temp
- GUI Windows-native via github.com/lxn/walk (TableView, TextEdit, PushButton)
- Meme fonctionnalites : check repos, pull, checkout, auto-update, logs
- build.bat : go build -ldflags "-H windowsgui -s -w" -> 9.6 Mo, zero dependance

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_internal/_tk_data/images/README

@@ -1,7 +0,0 @@
-README - images directory
-
-This directory includes images for the Tcl Logo and the Tcl Powered
-Logo.  Please feel free to use the Tcl Powered Logo on any of your
-products that employ the use of Tcl or Tk.  The Tcl logo may also be
-used to promote Tcl in your product documentation, web site or other
-places you so desire.