[201_93] fix \det input producing plain text instead of determinant matrix

[divyansharma001]

Summary

• Fix \det 输入出现纯文本，而不是行列式 #2931
• \det in math mode now inserts a determinant matrix (with | delimiters) instead of plain text "det"
• Changed (insert "det") to (make 'det) in latex-kbd.scm, consistent with menu and keyboard shortcut behavior

Test plan

• Open Mogan STEM, create new document, enter math mode
• Type \det, select from autocomplete, press Enter
• Verify a determinant matrix with vertical bar delimiters is inserted (not plain text)

[Copilot]

Pull request overview

Fixes Mogan STEM’s LaTeX input/autocomplete behavior so that \det in math mode inserts a proper determinant (vertical-bar delimited matrix) instead of the plain text det, aligning with the existing det macro and other insertion paths (menu/shortcuts).

Changes:

• Update LaTeX keyboard binding for det from plain text insertion to structured determinant creation.
• Add a development note documenting the issue, rationale, and manual test steps.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
TeXmacs/plugins/latex/progs/latex-kbd.scm	Switch det binding to (make 'det) to produce a determinant matrix structure.
devel/201_93.md	Document the bug, reasoning, fix, and how to test the corrected \det insertion behavior.

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