Fix zsh test stability runner script dependencies and npm script reference

- Create zsh-compatible common functions script (test-stability-common-zsh.sh)
- Fix script directory detection in zsh runner to use $(dirname "$0")
- Update zsh runner to source zsh-compatible common file instead of bash version
- Change npm script from test:playwright to test:web to match package.json
- Remove duplicate array declarations from zsh runner
- Make both scripts executable

Resolves "no such file or directory" and "command not found" errors when running zsh scripts.

scripts/test-stability-runner.zsh

@@ -5,16 +5,11 @@
 # Author: Matthew Raymer
 
 # Source common functions
-SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-source "${SCRIPT_DIR}/test-stability-common.sh"
+SCRIPT_DIR="$(dirname "$0")"
+source "${SCRIPT_DIR}/test-stability-common-zsh.sh"
 
 # Zsh-specific overrides and enhancements
-# Override associative array declarations for zsh compatibility
-typeset -A test_results
-typeset -A test_failures
-typeset -A test_successes
-typeset -A run_times
-typeset -A test_names
+# Note: Associative arrays are now defined in the common file
 
 # Enhanced progress tracking for zsh
 track_test_progress_enhanced() {