v0.6.29

Add Settings menu to set sparkline height (1-4 rows)

A new top-level Settings menu lets you make expanded sparklines taller for
finer vertical detail. render_analog_rows / render_digital_rows render the
spark across N text rows, stacking from the bottom (a present value always
keeps at least the bottom 1/8 so it never disappears; height 1 is byte-for-byte
the old single-row output).

The height is global: set_spark_height pushes it to every AnalogIn/DigitalIn
widget across all pages (authored and the runtime Auto page) and resizes each
expanded grid row to 1 + height. It persists to config.toml ([app]
spark_height) via write_layout and is restored on launch.

The four Settings items are click-only (no key hint): digits 1-3 are already
the column-layout shortcuts.

387 tests green; ruff + mypy clean.