mo.ui.date_range default value can fall outside its declared start/stop range #10648

Describe the bug

mo.ui.date_range produces a default value outside its own declared [start, stop] range when only one bound is given, unlike its mo.ui.date / mo.ui.datetime siblings which clamp correctly.

import marimo as mo, datetime as dt

# sibling clamps correctly:
mo.ui.date(start="2030-01-01").value          # date(2030, 1, 1) — in bounds

# date_range ignores the supplied bound:
mo.ui.date_range(start="2030-01-01").value    # (today, today) — BEFORE start
mo.ui.date_range(stop="2000-01-01").value     # (today, today) — AFTER stop

When exactly one of start/stop is provided and no explicit value, date_range falls back to (today, today) and ignores the bound, so the widget initializes out of its own range (and the None-value path skips the bounds validation the sibling widgets run).

Expected behavior

date_range should clamp its default to the supplied bound, matching date/datetime: start="2030-01-01" → (2030-01-01, 2030-01-01), stop="2000-01-01" → (2000-01-01, 2000-01-01).

Environment

marimo main; platform-independent.