fix(mosaic): make credential lifecycle transactional

packages/mosaic/framework/tools/git/git-credential-mosaic

@@ -32,6 +32,12 @@ done
 ident="$MOSAIC_GIT_IDENTITY"
 [ -z "$ident" ] && ident=$(git config --get mosaic.gitIdentity 2>/dev/null)
 [ -z "$ident" ] && ident="$username_in"
+if [ -n "${MOSAIC_AGENT_NAME:-}" ] && [ -n "$ident" ] && [ "$ident" != "$MOSAIC_AGENT_NAME" ]; then
+  echo "quit=true"
+  printf 'MOSAIC_CREDENTIAL_REFUSAL outcome=refused reason=provider-identity-mismatch identity=%s fleet_identity=%s host=%s shared_path_entered=false source=git-credential-mosaic\n' \
+    "$ident" "$MOSAIC_AGENT_NAME" "$host" >&2
+  exit 1
+fi
 if [ -n "$ident" ]; then
   case "$host" in
     git.uscllc.com)      idpfx=gitea-usc;;