fix: disable empty information saves

[arnestrickmann]

Summary

• Disable Save in new Address, Payment Card, and Note dialogs until at least one field contains a non-whitespace value.
• Guard form submission itself so keyboard or programmatic submission cannot create a blank Information record.
• Keep existing-record editing and agent-side forms unchanged.

Test Coverage

All changed paths are covered:

• requireNonEmpty with blank and whitespace-only values: Save disabled and submission blocked.
• requireNonEmpty with a real value: Save enabled and values submitted.
• Forms without requireNonEmpty: existing behavior preserved.
• /info Add dialogs: Address, Payment Card, and Note all opt into the guard.
• /info edit dialog: an existing empty record remains editable.

Tests: 47 → 49 (+2 new test files). AI-assessed changed-path coverage: 100%.

Pre-Landing Review

One informational test gap was found and fixed by adding route-level coverage. Testing, maintainability, performance, and code-structure reviews are otherwise clean.

Design Review

Design Review (lite): no findings. The change uses the shared Button component's existing native disabled state.

Eval Results

No prompt-related files changed, so evals were skipped.

Scope Drift

Scope Check: CLEAN. The diff is limited to the Information modal behavior and regression tests.

Plan Completion

No relevant plan file was detected.

Verification Results

• 374 tests passed, 0 failed.
• All package typechecks passed.
• Web app, docs, and website production builds passed.
• Manual /info flow was exercised locally before shipping.

TODOS

No root TODOS.md exists; no unrelated tracking file was added for this focused fix.

Test plan

• New Address starts with Save disabled.
• New Payment Card starts with Save disabled.
• New Note starts with Save disabled.
• Whitespace-only input keeps Save disabled.
• A non-whitespace value enables Save.
• Existing Information records remain editable.
• Full repository test suite passes.
• Production builds pass.