Revert "test(install): add a regression suite for install.sh + CI on Linux and macOS (#772)" (#827)

This reverts commit 1e2d1b940e.

.github/workflows/test-install.yml

@@ -1,30 +0,0 @@
-name: Test Installer
-
-# No path filter on purpose: the installer's contract can break from the other
-# side too — a renamed division, a file that loses its frontmatter, a change to
-# lib.sh — so these run on every PR.
-on:
-  pull_request:
-  push:
-    branches: [main]
-
-jobs:
-  test-install:
-    name: install.sh behavior (${{ matrix.os }})
-    runs-on: ${{ matrix.os }}
-    strategy:
-      fail-fast: false
-      matrix:
-        # macOS ships bash 3.2, Linux ships bash 5 — the scripts must pass on both.
-        os: [ubuntu-latest, macos-latest]
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Shell syntax
-        run: |
-          for f in scripts/*.sh; do bash -n "$f"; done
-
-      - name: Run installer tests
-        run: |
-          chmod +x scripts/test-install.sh scripts/install.sh
-          ./scripts/test-install.sh