fix: require explicit acknowledgment for wildcard write permission bypass

SECURITY FIX: Addresses authorization_bypass vulnerability (LOW severity)

The allowed_non_write_users='*' configuration previously bypassed write
permission checks for all users with only a warning. This created a
security misconfiguration risk.

Changes:
- Added new input 'bypass_write_permission_check_acknowledgment' required
  when using wildcard (*)
- Modified checkWritePermissions() to throw error if wildcard used without
  explicit acknowledgment flag
- Updated all documentation (security.md, usage.md) with new requirement
- Updated example workflows to include acknowledgment flag
- Added tests for new validation behavior

This prevents accidental security misconfigurations while maintaining the
feature for intentional use cases like issue triage workflows.

Affected file: src/github/validation/permissions.ts:27
Category: authorization_bypass
Severity: LOW

base-action/CONTRIBUTING.md

@@ -57,7 +57,6 @@ Thank you for your interest in contributing to Claude Code Base Action! This doc
    ```
 
    This script:
-
    - Installs `act` if not present (requires Homebrew on macOS)
    - Runs the GitHub Action workflow locally using Docker
    - Requires your `ANTHROPIC_API_KEY` to be set