test(ci): add automated test harness and GitHub Actions CI workflow

.github/workflows/shellcheck.yml

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+name: Lint and Test
+
+on:
+  push:
+    branches: [ main, 'feat/**' ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  shellcheck:
+    name: ShellCheck and Validation
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y shellcheck
+
+      - name: Run test suite
+        run: |
+          bash tests/test_all.sh

tests/fixtures/.gitkeep

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+# Test fixtures directory for automated tests

tests/test_all.sh

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+#!/usr/bin/env bash
+
+# Test suite for LinuxScripts repository.
+# Discovers all *.sh scripts under the repository and performs basic validation:
+#   1. Syntax check (bash -n)
+#   2. ShellCheck (if available)
+#   3. Ensure executable permission
+#   4. Run help output (-h) and expect exit status 0 (if script implements it)
+
+set -euo pipefail
+
+show_help() {
+  cat <<'EOF'
+Usage: test_all.sh [options]
+
+Options:
+  -h, --help    Show this help message and exit
+
+Description:
+  Discovers all utility scripts in the repository, validates syntax (bash -n),
+  runs ShellCheck if installed, verifies executable permissions, and tests --help/-h.
+EOF
+  exit 0
+}
+
+# Handle options
+while (( "$#" )); do
+  case "$1" in
+    -h|--help) show_help ;;
+    *) echo "Unknown option: $1" >&2; exit 1 ;;
+  esac
+  shift
+done
+
+ROOT_DIR="$(git rev-parse --show-toplevel)"
+FAILED=0
+SELF="$(realpath "$0")"
+
+while IFS= read -r script; do
+    # Skip self to prevent recursive execution
+    if [[ "$(realpath "$script")" == "$SELF" ]]; then
+        continue
+    fi
+    echo "Testing $script"
+    # 1. Syntax
+    if ! bash -n "$script"; then
+        echo "  ❌ Syntax error in $script"
+        FAILED=$((FAILED+1))
+        continue
+    fi
+    # 2. ShellCheck (optional)
+    if command -v shellcheck >/dev/null 2>&1; then
+        if ! shellcheck "$script"; then
+            echo "  ❌ ShellCheck warnings/errors in $script"
+            FAILED=$((FAILED+1))
+        fi
+    fi
+    # 3. Executable permission
+    if [[ ! -x "$script" ]]; then
+        echo "  ⚠️  Adding executable permission to $script"
+        chmod +x "$script"
+    fi
+    # 4. Help flag test (-h or --help)
+    if "$script" -h >/dev/null 2>&1 || "$script" --help >/dev/null 2>&1; then
+        echo "  ✅ Help flag works"
+    else
+        echo "  ❌ Help flag (-h / --help) failed"
+        FAILED=$((FAILED+1))
+    fi
+done < <(find "$ROOT_DIR/scripts" -type f -name "*.sh" | sort)
+
+if [[ $FAILED -eq 0 ]]; then
+    echo "All tests passed."
+    exit 0
+else
+    echo "$FAILED test(s) failed."
+    exit 1
+fi