Count wide back-wall rebounds as backboard bounces

[colonelpanic8]

Summary

• widen backboard-bounce detection to include full back-wall/corner reads instead of only central backboard bounces
• add a regression test for a wide high back-wall rebound that should arm double-tap detection

Root cause

The backboard-bounce detector capped rebounds at abs(x) <= 1600, so wide back-wall reads could never produce the upstream backboard event needed by the double_tap and double_tap_goal paths.

Validation

• cargo fmt --check
• cargo test -p subtr-actor backboard_bounce::tests
• cargo test -p subtr-actor double_tap::tests
• cargo test -p subtr-actor --test clip_double_tap_test
• just check