Require hook_dom in node_map components

[Copilot]

• Explore the codebase to understand the issue
• Add debug assertion to enforce hook_dom in node_map item components
• Update README documentation with the new requirement
• Simplify node_map reordering code relying on the new rule
  • Removed instance_dom_last_get function
  • Removed instance_reinsert function
  • Simplified reordering to directly use child.dom
• Remove redundant child.dom && checks now that hook_dom is enforced
• All tests pass

Original prompt

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This section details on the original issue you should resolve

<issue_title>Require hook_dom in node_map component</issue_title>
<issue_description>Currently, components given to node_map can contain multiple nodes without a wrapper element.
I think that this makes reordering in node_map way more complicated.
See if there is a stable and efficient way to still allow node_map components to not have a hook_dom. If you found one, abort and do nothing but commenting me your result.
Otherwise, add a debug assertion to the node_map handler enforcing its dynamic children to all have a direct dom element. If you did that, also mention it in the readme and make sure no test case or example violates this new rule.
See if the node_dom handler code could be simplified relying on the new rule.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Require hook_dom in node_map component #61

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[Copilot]

Pull request overview

This PR enforces that components used with node_map must call hook_dom() to define their root DOM element, enabling significant simplification of the reordering logic.

Changes:

• Added debug assertion to catch missing hook_dom() calls in node_map components
• Simplified reordering by replacing recursive DOM traversal with direct child.dom access
• Removed ~50 lines of workaround code (instance_dom_last_get and instance_reinsert)
• Added documentation to README explaining the new requirement

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/lui.js	Added debug assertion for hook_dom requirement; simplified reordering logic; removed recursive DOM traversal functions
README.md	Documented that node_map components must use hook_dom

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[L3P3]

Not cleaned up enough.

[L3P3]

This condition is not needed anymore, right?
Also look for other similar cases around here.
We rely on child.dom existing!

[Copilot]

Correct. Removed all redundant child.dom && checks (lines 983, 991) and simplified the dom_first assignment (lines 1026-1030) since we now rely on child.dom always existing. Addressed in b916bd8.