fix: only show code action when there's no sum

Tighten the ADDITION regex so that the 'Evaluate' code action only appears if there's no sum. Previously, after using the action, the lightbulb remained visible in VSCode and would keep appending the sum to the line, resulting in things like `1 + 1 = 2! 2! 2!`

examples/servers/code_actions.py

@@ -29,7 +29,7 @@
 )
 
 
-ADDITION = re.compile(r"^\s*(\d+)\s*\+\s*(\d+)\s*=")
+ADDITION = re.compile(r"^\s*(\d+)\s*\+\s*(\d+)\s*=\s*$")
 server = LanguageServer("code-action-server", "v0.1")