test: cover input component, option funcs, and app/reader plumbing

Raises root package coverage from 75.1% to 81.9%. Adds full coverage of
input.go and input_options.go (previously 0%), the App and TextArea
option funcs, the escape sequence builders, key matcher specs, layout
edge/rect helpers, event App accessors, BlurFocused, EventQueue, and
stdin reader pause/resume/interrupt behavior. NewApp success paths need
a real TTY and stay uncovered.