refactor(engine): extract formatLabelValue shared helper for bar/column/dot

Consolidates a byte-identical 4-line value formatter that was duplicated
across bar, column, and dot label modules into
packages/engine/src/charts/_shared/format-label-value.ts.

Font sizes (11 in bar/dot, 10 in column), LABEL_FONT_WEIGHT, the
bar-only parseDisplayNumber / SUFFIX_MULTIPLIERS, and density filter
logic are intentionally left local because they diverge or will be
consolidated separately in a later step.

Pure dedup: no behavior change, all 1792 tests pass, all 8 visual
baselines match with zero pixel drift.

Author: rileyhilliard

packages/engine/src/charts/_shared/format-label-value.ts

@@ -0,0 +1,15 @@
+/**
+ * Shared numeric value formatter for data labels.
+ *
+ * Used by bar, column, and dot label computation to display a value:
+ * abbreviated (K/M/B/T) for magnitudes >= 1000, otherwise the default
+ * numeric format.
+ */
+
+import { abbreviateNumber, formatNumber } from '@opendata-ai/openchart-core';
+
+/** Format a label value for display (abbreviate large numbers). */
+export function formatLabelValue(value: number): string {
+  if (Math.abs(value) >= 1000) return abbreviateNumber(value);
+  return formatNumber(value);
+}

packages/engine/src/charts/bar/labels.ts

@@ -18,24 +18,17 @@ import type {
   ResolvedLabel,
 } from '@opendata-ai/openchart-core';
 import {
-  abbreviateNumber,
   buildD3Formatter,
   estimateTextWidth,
-  formatNumber,
   getRepresentativeColor,
   resolveCollisions,
 } from '@opendata-ai/openchart-core';
+import { formatLabelValue } from '../_shared/format-label-value';
 
 // ---------------------------------------------------------------------------
 // Helpers
 // ---------------------------------------------------------------------------
 
-/** Format a bar value for display (abbreviate large numbers). */
-function formatBarValue(value: number): string {
-  if (Math.abs(value) >= 1000) return abbreviateNumber(value);
-  return formatNumber(value);
-}
-
 /** Suffix multipliers mirroring core's abbreviateNumber output (K/M/B/T). */
 const SUFFIX_MULTIPLIERS: Record<string, number> = {
   K: 1_000,
@@ -124,7 +117,7 @@ export function computeBarLabels(
     if (formatter && Number.isFinite(rawNum)) {
       valuePart = formatter(rawNum);
     } else if (Number.isFinite(rawNum)) {
-      valuePart = formatBarValue(rawNum);
+      valuePart = formatLabelValue(rawNum);
     } else {
       // Fallback: extract from aria label
       const ariaLabel = mark.aria.label;

packages/engine/src/charts/column/labels.ts

@@ -18,23 +18,12 @@ import type {
   ResolvedLabel,
 } from '@opendata-ai/openchart-core';
 import {
-  abbreviateNumber,
   buildD3Formatter,
   estimateTextWidth,
-  formatNumber,
   getRepresentativeColor,
   resolveCollisions,
 } from '@opendata-ai/openchart-core';
-
-// ---------------------------------------------------------------------------
-// Helpers
-// ---------------------------------------------------------------------------
-
-/** Format a column value for display (abbreviate large numbers). */
-function formatColumnValue(value: number): string {
-  if (Math.abs(value) >= 1000) return abbreviateNumber(value);
-  return formatNumber(value);
-}
+import { formatLabelValue } from '../_shared/format-label-value';
 
 // ---------------------------------------------------------------------------
 // Constants
@@ -82,7 +71,7 @@ export function computeColumnLabels(
     if (formatter && Number.isFinite(rawNum)) {
       valuePart = formatter(rawNum);
     } else if (Number.isFinite(rawNum)) {
-      valuePart = formatColumnValue(rawNum);
+      valuePart = formatLabelValue(rawNum);
     } else {
       // Fallback: extract from aria label
       const ariaLabel = mark.aria.label;

packages/engine/src/charts/dot/labels.ts

@@ -18,23 +18,12 @@ import type {
   ResolvedLabel,
 } from '@opendata-ai/openchart-core';
 import {
-  abbreviateNumber,
   buildD3Formatter,
   estimateTextWidth,
-  formatNumber,
   getRepresentativeColor,
   resolveCollisions,
 } from '@opendata-ai/openchart-core';
-
-// ---------------------------------------------------------------------------
-// Helpers
-// ---------------------------------------------------------------------------
-
-/** Format a dot value for display (abbreviate large numbers). */
-function formatDotValue(value: number): string {
-  if (Math.abs(value) >= 1000) return abbreviateNumber(value);
-  return formatNumber(value);
-}
+import { formatLabelValue } from '../_shared/format-label-value';
 
 // ---------------------------------------------------------------------------
 // Constants
@@ -81,7 +70,7 @@ export function computeDotLabels(
     if (formatter && Number.isFinite(rawNum)) {
       valuePart = formatter(rawNum);
     } else if (Number.isFinite(rawNum)) {
-      valuePart = formatDotValue(rawNum);
+      valuePart = formatLabelValue(rawNum);
     } else {
       // Fallback: extract from aria label
       const ariaLabel = mark.aria.label;