You are confusing AOA with sink rate. The sink rate is the same across
the airfoil, but AOA is dependent on sink rate and forward speed, so:

If an airfoil has a forward motion of 10 and sink rate of one, then
its angle of attack can be measured -- about 5.7 degrees. If we then
slowed its forward speed to 9 while maintaining a sink rate of 1, the
angle of attack would be higher: 6.3 degrees.

We agree that the angular speed is the same across the span. We agree
"that the inner wing is flying slower." The sink rate is the same
across the span. As you've stated, this is a given: the wings are
fixed to one another. Since AOA is dependent on both sink rate and
forward speed, then the inside wingtip must have a higher AOA.

Inner wing slower, higher AOA. Outer wing faster, lower AOA. Lift is
dependent on both AOA and speed. So even though the outer wing is at a
lower angle of attack, it is moving through the air more rapidly, and
producing slightly more lift than the inner wing. With resulting
overbanking tendency.

Balance this knowledge against the sailplane's response to a turning
stall. Inner wingtip typically drops first. Why? Because it has a
higher AOA. No aggrevation from the aileron required.