Remove the depth-2 cap in walk_meta_inputs so every fetched input
at every depth is surfaced, not just two levels (issue #275). The
uncapped walk needs a guard: a visited-node set makes it a spanning
tree — each fetched node walked once, at its shallowest path — so
shared subtrees don't re-walk and a cycle can't recurse forever.
A two-pass walk (claim a node's direct inputs before descending)
keeps shallow inputs at a shallow path.
Frontend: renderMetaInputs indents each row by its slash-path depth
and shows the leaf segment (full path on hover), plus a select-all /
select-none control so a long input list isn't ticked box by box.
7f97acf19e