tighten Node.parent to Collector and resolve the resulting typing issues

[RonnyPfannschmidt]

Can this be Collector? (Although would be a typing breaking change for from_parent...)

Originally posted by @bluetech in #8037 (comment)

[RonnyPfannschmidt]

I asked Claude Opus 5 (via Claude Code) to check whether this issue is still live. The investigation and the text below are its work; I read it and I am posting it.

Resolved by #14758.

Node.parent is now annotated Collector | None (src/_pytest/nodes.py:152), and Collector.from_parent takes parent: Collector (nodes.py:219) — the tightening this issue asked for. The change landed as part of "Replace string nodeids with a structured NodeId internally" (431f3e1), which is why it was never linked here.

Closing as resolved.