CSIntro updates - June 2025

[ganicke]

Merge in the course updates for 'CSIntro' from Douglas and Mary Kiang. This is a move of the staged content from the ./test/courses folder to the regular doc tree.

I'm leaving the ./test/courses/csintro staged stuff intact until we're OK with the update. It can get scrubbed in a later PR.

Notes (items to clarify):

• Should probably review the size and presentation of the new images in 'Accelerometer'. *Done in 36a14e3.
• In 'Final Project', is the project[classroom] page a replacement for the older project page or an additional resource? I took it as a replacement.

Closes #6319

[Jaqster]

Thanks so much Galen!