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

docs/migration-guide.md

@@ -228,12 +228,10 @@ jobs:
 The action now automatically detects the appropriate mode:
 
 1. **If `prompt` is provided** → Runs in **automation mode**
-
    - Executes immediately without waiting for @claude mentions
    - Perfect for scheduled tasks, PR automation, etc.
 
 2. **If no `prompt` but @claude is mentioned** → Runs in **interactive mode**
-
    - Waits for and responds to @claude mentions
    - Creates tracking comments with progress