Fixes 12697: Document readonly inputs

BS3 commits: e418377b119cbe8604370adcc17ab3de76b2a415
clarify deprecation /cc @cvrebert

BS3 commits: 13ed379767d19040c98fc23bd9b5cdb84e66474b
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BS3 commits: fdbeefff590d2c185eae86f2e5976c5e8d0de28d
Fixes 12848: Account for and document progress bars at 0-3%

BS3 commits: 24de9b099438c09236b2066333744e3995cd88ab