Add @goodwidget/savings-widget with SDK-backed deposit/withdraw flows and Storybook coverage

[Copilot]

• Review issue requirements, architecture docs, and demo-environment guidance
• Run baseline install/lint/build/tests to capture pre-existing status
• Scaffold packages/savings-widget with package config, tsup/tsconfig, and public exports
• Implement provider-driven onboarding, deposit, and withdraw flows using @goodsdks/savings-sdk (no local savings-sdk package)
• Add focused tests for key widget states/flows
• Add Storybook story and demo smoke coverage for SavingsWidget
• Run targeted validation (build/lint/tests) for changed areas
• Run parallel validation and finalize
• Updated SavingsWidget UI screenshot:

SavingsWidget UI

[Copilot]

@sirpy Unfortunately, I hit an error while trying to use the custom Copilot setup steps configured for this repository and had to close this PR. The error I am seeing is:

no `copilot-setup-steps` job found in your `copilot-setup-steps.yml` workflow file. Please ensure you have a single job named `copilot-setup-steps`. For more details, see https://gh.io/copilot/actions-setup-steps

Once you or someone with the necessary access fixes the problem, please unassign and then reassign issue #0 to me and I'll retry. Thanks!

[Copilot]

@sirpy Thanks for sending me some feedback. Unfortunately, I hit an error while trying to use the custom Copilot setup steps configured for this repository. The error I am seeing is:

no `copilot-setup-steps` job found in your `copilot-setup-steps.yml` workflow file. Please ensure you have a single job named `copilot-setup-steps`. For more details, see https://gh.io/copilot/actions-setup-steps

Once you or someone with the necessary access fixes the problem, please let me know in a comment and I'll try again. Thanks!