fix(completion): harden bash COMP_WORDBREAKS handling and test

Make the compspec tolerate unset COMP_WORDBREAKS and helper failures, and
drive the integration test through the same Python entrypoint as other
completion tests so the autocomplete env var matches.

Author: yoshibase

typer/_completion_shared.py

@@ -29,8 +29,8 @@ class Shells(str, Enum):
 
     local IFS=$'\n'
     local -a __raw
-    __raw=( $( env COMP_WORDS="${__words[*]}" \\
-                   COMP_CWORD=$__cword \\
+    __raw=( $( env COMP_WORDS="${__words[*]}" \
+                   COMP_CWORD=$__cword \
                    %(autocomplete_var)s=complete_bash $1 ) ) || true
 
     local __wordbreaks="$COMP_WORDBREAKS"