feat: add sandbox mode, pre-flight checks, and rollback to release.sh

  - Add --sandbox flag to test releases in isolated temp directory
  - Add --force flag to skip confirmations (for CI automation)
  - Add --json flag for machine-readable output
  - Add --verbose flag for detailed logging
  - Add --rollback flag to restore from backup
  - Add pre-flight checks (gh auth, git clean, required files, etc.)
  - Add automatic backup/rollback on failure
  - Add proper exit codes (0=success, 1=validation, 2=execution)
  - Redirect all logs to stderr, only JSON to stdout
  - Add tests for new functionality

Author: Chemaclass

.gitignore

@@ -20,6 +20,7 @@ report.html
 local/
 tmp/
 dev.log
+.release-state/
 
 # ai
 .tasks/