Trace-to-root on a clean value: follow same-bits inputs first

When a backward 'trace to root' over RTL plus a waveform also handles values with no x/z, choosing the data input whose value is oldest (the rule that works for x) picks wrong for muxes: for q <= ld ? d : q at a load, the old q (from reset) is oldest, though the value came from d. Prefer the data input whose bits equal the traced value exactly, and fall back to oldest only when none match. Don't count a match that only holds after stripping leading zeros on a 1-bit input: a select line of value 1 then 'equals' an 8-bit 00000001 and the chain wanders into the select's driver. If the fan-in roles mark ternary selects as data, that last guard matters.