fix: refit terminal after sidebar toggle animation completes

toggleSidebar() flipped the sidebar--collapsed CSS class but never told
xterm.js to recalculate its dimensions. The terminal canvas kept its old
column/row count until a new session was opened (which creates a fresh
terminal that measures correctly on first fit()).

Fix: expose window._refitTerminal() from terminal.js, then call it via
a transitionend listener in toggleSidebar() so the terminal refits once
the 250ms CSS width/transform transition finishes.

Bumps version to 0.4.5.

uv.lock

@@ -332,7 +332,7 @@ wheels = [
 
 [[package]]
 name = "muxplex"
-version = "0.4.4"
+version = "0.4.5"
 source = { editable = "." }
 dependencies = [
     { name = "aiofiles" },