Hi Srinivas,
I had one such requirement, (though not a runmode to be fetched in a rule editor) , but some configuration properties based on the run mode to be fetched. These configuration properties were saved as per individual run modes in respective OSGI configs, which were fetched in clientlibs via clientside requests like Ajax or Fetch (HTTP requests), and the resultant data(JSON in my case) got utilized in scripts, be it in rule editor or in clientlib.
Likewise, if a configuration property denoting the runmode can be saved in respective OSGIconfig JSON files, then runmode, can be obtained via aforementioned approach.
Only caveat, in my opinion is the exposure of these obtained data in browser's network tab plus a network call made. However, if those runmodes can be represented by your custom abbreviations, then this approach can work.
Hopefully, this helps!