Subtheme not reading CSS

I can't get the theme to pick up the CSS - this includes the "foundation" style.css, as well as the style-custom.css I'm trying to add as per the below. ("Subtheme" is not the actual name, BTW.) The only CSS that's getting picked up are the SASS files, which start with an underscore.

Below is the hierarchy; I believe everything is in the right place, including indentation. Could this be a permissions issue? Tearing my hair out here - any assistance greatly appreciated... thanks in advance!

Problem/Motivation

Subtheme isn't picking up CSS

Steps to reproduce

Subtheme structure is as follows:

[bootstrap_subtheme]

---[bootstrap_subtheme.info.yml]

--file contents--

-----name: 'Bootstrap Subtheme'
-----type: theme
-----description: 'Bootstrap subtheme based on Bootstrap 5 theme.'
-----core_version_requirement: '^8.9 || ^9'
-----'base theme': bootstrap5
-----libraries:
----- - bootstrap_subtheme/global-styling
-----stylesheets-remove:
----- - '@bootstrap5/css/style.css'

---[bootstrap_subtheme.libraries.yml]

--file contents--

-----global-styling:
------css:
--------theme:
----------css/style.css: {}
----------css/style-custom.css: {}

--[css]
---style.css
---style-custom.css

[bootstrap5]