v0.6.0

0.6.0

• feat: add sdk command to install and manage multiple Flutter SDK versions (sdk install, sdk list, sdk remove)
• feat: add dr alias for doctor and up alias for update
• refactor: replace all exit() calls in shared utilities with FlutterCompileException
• refactor: add centralized exception handling in command runner
• refactor: extract shell config detection to shared F.getShellConfigPath() utility
• refactor: replace exit() calls with return exit codes in install/build commands
• fix: rename uninstall devtool → uninstall devtools for consistency (old name kept as alias)
• test: extract shared test helpers to reduce boilerplate across 12 test files
• test: add tests for exception handling, sdk command, install, uninstall, and switch commands