fix(pulse): promote rounded compact values to their correct unit

[MarekPoskrobko]

What & why

Closes #344.

Money Pulse now promotes compact values when rounding crosses a unit boundary:

• 999.6 becomes 1.0k, not 1000
• 999950 becomes 1.00M, not 1000.0k

Type of change

• Fix
• Feature
• Improvement
• Docs
• Infra / chore (no user-visible effect)

Definition of done

• Code is fully wired and reachable by the user. No dead paths, stubs, TODOs, or commented-out code.
• No mocks, fake data, or placeholder values. Real APIs and real data only.
• Every interactive element has hover, active, and focus states (not a UI control change).
• Loading, empty, and error states are designed and helpful (not a UI state change).
• npm test passes and npm run typecheck is clean. Repository-wide failures outside this PR were observed locally, so this remains unchecked.
• npm run lint is clean (or only pre-existing warnings). Repository-wide errors outside the changed files were observed locally, so this remains unchecked.
• I reviewed my own git diff. Every changed line is justified.

Validation

• npx vitest run tests/pulse-format.test.js — 5/5 tests passed.
• npm run build:pages — passed.
• npm run check:rules -- --base 8a1fd5dbd1078e4da94c666390a5d142e2afb135 --head HEAD — passed.
• git diff --check — passed.
• Pre-push rule and secret checks — passed.

Changelog

• Added a data/changelog.json entry.

Screenshots / recordings

Not applicable. This change adjusts compact numeric labels and is covered by unit tests.