Step whole characters everywhere instead of assuming 1 byte = 1 char, so the dead-key composer's accented Latin-9 output (é, ç, …) no longer traps the caret mid-character and panics on the next edit. Covers h/l/a and the Escape step-back, j/k column math, backspace and x, word-end (e) with de/ce, and layout/caret_rc (byte offsets vs display columns). Adds 7 accented-input tests (15 total).