There is no evidence for any of it. The 1907 Gazetteer you are citing says that the Kasis have a tradition that they migrated from Takht-i-Sulaiman seven centuries ago. However, you should keep in mind that all Pashtun tribes had such traditions. Even the Abdalis (Durranis) 1/4

Note that even kites in the Basant used to be specifically of yellow colour. The page is from The Indian Listener, Vol. IV. No. 2. (7th January 1939). It mentions it as a Hindu festival but does say that all communities of Lahore celebrate it.

A Khan of Kalat in the 19th century himself provided the information that the Raisanis are of Afghan (Pashtun) descent. Tarikh-i-Baluchistan by Hattu Ram also attributes Tarin Pashtun roots to the Raisanis. Source: 'The Brahui langauge' (1909) by Denys Bray.

Farzana Ali Farzana Ali badly wants to celebrate basant in Peshawar.

Langah was indeed a Sindhi dynasty. The founder of the Langah dynasty is referred to as a "Sindi" from Lehri (in Balochistan province) by the author of Tarikh-i-Haqqi (c.1605 AD). A significant portion of the population in the Lehri tehsil continues to speak Sindhi to this day.

Ranjit Singh dressed entirely in yellow for the festival of Basant, 1835 (c). Ranjit Singh’s entire army would wear yellow for Basant. Common folk were also urged to dress in yellow for the festival, and yellow kites would be flown. Victoria a& Albert Museum.

The only region of Pakistan that is truly civilized and has a sense of hygiene similar to that of Iranians and Tajiks is Gilgit-Baltistan. However, GB is on a fast track to becoming very 'Pakistan-ish' and Desi, and will resemble these Hindi slum dwellers of Karachi in the future