[bug] Number formatting: large amounts (e.g. ARR) shown without M/K suffix

[ClaireGz]

Problem

Large monetary values returned by the agent (e.g. ARR figures in the millions) are rendered as raw numbers — 12345678 rather than $12.3M or 12,345,678. Hard to read at a glance and looks unpolished next to comparable BI tools.

Expected

When the number is too large, compact it by default
NB: option might be available thanks to the coming interactive charts feature

[shashank-poola]

Analysis & Proposed Fix

Root cause: The codebase already has a working compact number formatter (formatYAxisTick) in apps/shared/src/chart-builder.tsx that correctly outputs K/M/B suffixes, but it's only wired to Y-axis tick labels on charts. Every other number display surface uses the raw .toLocaleString() call, which produces 12,345,678 instead of 12.3M.

Affected locations:

apps/shared/src/chart-builder.tsx line 167 - KPI card (frontend React), shows 12,345,678 raw
apps/shared/src/chart-builder.tsx line 381 - Pie chart slice labels, raw value with no formatting at all
apps/backend/src/utils/story-html.tsx line 187 - KPI card (backend/email HTML), shows 12,345,678 raw
apps/backend/src/utils/story-html.tsx lines 353, 443 - Chart tooltip script (formatVal + total), shows 12,345,678 raw
apps/frontend/src/components/ui/chart.tsx lines 216, 230 - Chart tooltip values + total shows 12,345,678 raw

Proposed fix:

1. Extract the existing compact logic into a single shared utility formatCompactNumber(value: number): string. Thresholds stay exactly as they are today - ≥1B → B, ≥1M → M, ≥10K → K, below that → comma-separated.

2. Make formatYAxisTick a thin wrapper around it zero behavior change for existing charts.

3. Apply formatCompactNumber to all 5 affected sites above — KPI cards, pie labels, and chart tooltips in both the frontend React components and the backend HTML renderer.

What this does NOT change:

• Data tables (story-table-utils.ts), intentionally left as-is. Analysts need exact numbers in tabular data.
• No $ currency prefix SeriesConfig has no format or unit field, so the system has no reliable way to know whether a value is monetary vs. a count or ratio. Adding it heuristically would cause false positives on non-currency metrics.

Scope: ~40 lines changed across 3 files. Happy to open a PR if the approach looks good to maintainers.

[shashank-poola]

@Bl3f - submitted a fix in PR #766. Extracted the existing formatYAxisTick logic into a shared formatCompactNumber utility and applied it across all 6 affected surfaces. 16 unit tests passing. Happy to iterate on any feedback.