Left-arrow "human-cadence" absorb now logs telemetry instead of being silent

Claude Code has a gesture where pressing the left arrow key can be "absorbed" (ignored) if it lands inside a short confirmation window, meant to avoid reacting to presses that are too close together for a human to have intended. Previously this absorption happened silently. Now it records a tengu_left_arrow_blocked telemetry event with the reason absorb and how many milliseconds had passed since the previous press, plus a debug log message, and this only fires once per absorption window so it doesn't spam repeated events.