The topology doc keeps its filename and its second half (manager
special-casing, harness unit shape) — both are cross-referenced from
other pages and neither is about the parent field. Its first half is
rewritten: what topology.json is now, and a table of what the removal
took with it, so a reader who finds `<parent>` or `set-parent` in an old
issue thread learns it went away rather than moved.
The dashboard's tree-rendering section is marked dormant rather than
deleted: the walk is still in swarm.js and retiring it is the frontend
owner's call.
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