fix(tests): repair framework paths, assertions, and arithmetic

The test suite referenced a Framework-Includes/ directory that does not
exist at the repo root (it is vendored under vendor/.../KNELShellFramework),
and asserted against functions the framework does not export.

- Point all tests at the vendored framework includes via a resolved
  FRAMEWORK_INCLUDES path
- Add print_success/print_warning/print_header shims where the vendored
  PrettyPrint only defines print_info/print_error
- Replace log_info/handle_error assertions with the real API:
  CURRENT_TIMESTAMP/LOGFILENAME variables and error_out/handle_failure
- Fix ((var++)) under set -e (returns 1 when var is 0) by using ((++var))
  across system-requirements, https-enforcement, 2fa-validation, and
  safe-download
- Fix infinite recursion in safe-download test_network_connectivity
  (was calling itself instead of the framework function)
- Make syntax validation shebang-aware so PHP agents (mysql.sh) are
  skipped instead of flagged as bash syntax errors

Framework unit test now passes (exit 0).

🤖 Generated with [Crush](https://github.com/charmassociates/crush)

Assisted-by: GLM-5 via Crush <crush@charm.land>

Project-Tests/run-tests.sh

@@ -5,10 +5,19 @@
 
 set -euo pipefail
 
-# Source framework includes
-PROJECT_ROOT="$(dirname "$(realpath "${BASH_SOURCE[0]}")")/.."
-source "$PROJECT_ROOT/Framework-Includes/Logging.sh"
-source "$PROJECT_ROOT/Framework-Includes/PrettyPrint.sh"
+# Resolve repository root from this script's location (Project-Tests/ -> repo root)
+PROJECT_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+# The KNELShellFramework is vendored under vendor/
+FRAMEWORK_INCLUDES="$PROJECT_ROOT/vendor/git@git.knownelement.com/29418/KNEL/KNELShellFramework/Framework-Includes"
+source "$FRAMEWORK_INCLUDES/Logging.sh"
+source "$FRAMEWORK_INCLUDES/PrettyPrint.sh"
+
+# The vendored PrettyPrint only defines print_info/print_error; provide the
+# additional output helpers the test suite relies on.
+function print_header()  { echo ""; echo "=== $1 ==="; }
+function print_success() { echo "✅ $1"; }
+function print_warning() { echo "⚠️  $1"; }
 
 # Test configuration
 TEST_LOG_DIR="$PROJECT_ROOT/logs/tests"