When an explicit profile was requested and LoadMultiAppConfig failed, the
error was discarded and every failure reported as profile_not_found,
masking a real config problem (e.g. malformed file) behind a misleading
"run profile list" hint. Propagate the underlying error when it is a
malformed-config failure (errors.Is ErrMalformedConfig) so errors.Is /
errors.Unwrap keep working, mirroring the no-profile branch. An absent
config is not malformed and still yields the friendly profile_not_found.
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