feat(sdk-app): replace entity ID inputs with searchable selects

[aaronlee777]

Summary

Updates the SDK dev app's demo settings panel so users no longer need to know UUIDs to switch the active employee, contractor, or payroll. The entity ID text inputs are replaced with searchable two-line comboboxes populated from the API, and every entity row gains a Copy ID button.

Changes

• Employee, Contractor, and Payroll IDs are now searchable comboboxes listing entities for the current company. Each option shows a primary label (employee/contractor name or payroll period) and the UUID below it in a muted monospace style.
• Lists are fetched on panel open from /api/v1/companies/{companyId}/{employees,contractors,payrolls} when the proxy is in flow-token mode. When the proxy is unavailable, each combobox gracefully falls back to a plain text input.
• Company ID becomes a read-only field.
• Every entity row (Company, Employee, Contractor, Payroll, Request ID, Form ID) gets a Copy ID button with a "Copied" confirmation state.
• Adds combobox/helper-line/copy-row styles to DemoSettingsPanel.module.scss.
• New helpers extracted to entityFormatters.ts (label formatting) and useEntityCatalog.ts (fetching/caching the entity lists).

Open/close behavior

• Clicking the input toggles the menu open and closed.
• Clicking anywhere outside the input (label, copy button, panel background, other fields) closes the menu.
• The selected entity name stays in the DOM (hidden via visibility while the menu is open) so opening the menu does not shift content below.
• The menu anchors flush below the input rather than below the helper line.

Demo

Testing

• npm run sdk-app
• Open the demo settings panel and verify:
  • Company ID is read-only and the Copy button copies the UUID (shows "Copied" briefly).
  • Employee, Contractor, and Payroll fields show comboboxes with two-line options (name/period + UUID).
  • Selecting an option updates the active entity ID and the Update button appears.
  • Every entity row (including Request ID and Form ID) has a working Copy ID button.
  • Clicking the input toggles the menu; clicking anywhere outside (label, copy button, etc.) closes it.
  • Pressing Escape closes the menu.
  • Opening/closing the menu does not shift the fields below.
  • When running without a flow token, the three combobox fields gracefully fall back to text inputs.

🤖 Generated with Claude Code