[Test] Add Zero-Value Expense Test Case to Finance Discipline Test Suite

• Labels: good first issue, testing, difficulty:beginner, area:core
• Target File: tests/finance-discipline.test.ts
• Estimated Time: 10–15 minutes
• Difficulty: Level 2 (Beginner)

Why This Matters

Financial arithmetic in PACT OS requires strict boundary handling. Verifying that zero-value cents format correctly ensures financial ledgers render cleanly without negative sign zero (-$0.00) bugs.

Current Behavior

tests/finance-discipline.test.ts tests positive and negative cent allocations, but does not explicitly assert zero-cents formatting.

Requested Change

Add a test case in tests/finance-discipline.test.ts asserting that formatCentsToCurrency(0) returns "$0.00" and handles zero allocations without error.

Acceptance Criteria

• Zero-value assertion added to tests/finance-discipline.test.ts.
• Test suite executes cleanly offline with npm run test:file -- tests/finance-discipline.test.ts.

Verification

npm run test:file -- tests/finance-discipline.test.ts

Contributor Notes

Single-file test addition.

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Open tests/finance-discipline.test.ts and review the existing positive and negative cent allocation cases. Add the zero-value assertion for formatCentsToCurrency(0), then run npm run test:file -- tests/finance-discipline.test.ts and confirm the suite passes offline.