fix(maths): scale-minmax-table fails on current Nu (undefined column2, deprecated merge)

[tonythethompson]

What's broken

scale-minmax-table in modules/maths/math_functions.nu fails on current Nu (tested on 0.113.1) for two independent reasons:

1. column2 is undefined in this module. It's only defined in sourced/misc/nu_defs.nu (an unrelated personal-dotfiles file elsewhere in this repo). scale-minmax-table calls it without importing or defining it locally, so it only ever worked in a shell session where nu_defs.nu happened to already be sourced separately. As a standalone module command, it's always been broken.
2. merge {$it} is no longer valid. merge used to accept a closure form; current Nu's merge takes a record/table value directly (see help merge). This fails to parse on recent Nu regardless of the column2 issue.

Fix

• Add a local column2 helper (same implementation as the one in sourced/misc/nu_defs.nu) so this module doesn't depend on an unrelated file being sourced first.
• merge {$it} -> merge $it.

How I found this

I was evaluating this module as a candidate seed package for an unrelated project's package registry and ran it against a real Nu 0.113.1 instead of trusting the source — it failed to parse. Diagnosed both root causes from there.

Verification

On Nu 0.113.1:

• The whole module now parses cleanly (it did not before).
• [[a b]; [1 10] [2 20] [3 30]] | scale-minmax-table 0 1 produces correct per-column min-max scaling:

  ╭───┬──────┬──────╮
  │ # │  a   │  b   │
  ├───┼──────┼──────┤
  │ 0 │ 0.00 │ 0.00 │
  │ 1 │ 0.50 │ 0.50 │
  │ 2 │ 1.00 │ 1.00 │
  ╰───┴──────┴──────╯
  

• Spot-checked root, croot, and delta in the same file still produce correct output, unaffected by this change.

[Copilot]

Pull request overview

Fixes scale-minmax-table in the maths module so it works on current Nushell by removing an implicit dependency on an unrelated sourced file and updating a now-invalid merge syntax.

Changes:

• Added a local (non-exported) column2 helper to make scale-minmax-table self-contained.
• Updated merge {$it} to merge $it to match current Nushell merge parsing/usage.

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[fdncred]

Thanks!