We have ruled India for 1000 years

At what point does one become a Punjabi? Starting with the Ghauris and the Mamluks, we start to see rulers of Afghan/Central Asian ancestry shifting their capitals to Lahore and settling in the Subcontinent. When to they cease to be “foreigners?”

Probably one of the worst examples you could have chosen. Sind has an extensive history of self-rule. At various points throughout the past 1000 years it was ruled by the native Sindhi Soomro Dynasty, who were followed by the native Sindhi Samma Dynasty - essentially spanning a 500 year period of native rule between them.