Chart builder: intent front door, Heatmap mark, role-aware guidance

.claude/skills/alignment/SKILL.md

@@ -134,9 +134,19 @@ Review all changes in scope. If changes span multiple patterns below, apply all
     case, active voice, no "please", no exclamation marks in errors). If/when an i18n layer
     exists, route strings through it instead of hardcoding.
 
+15. **Chart-builder guidance reasons over role, not raw type** (`src/core/chart-builder.ts`):
+    a `builderWarnings` rule (or any measure/dimension decision) must ask the post-transform
+    **role** via the shared predicates (`isMeasureMapping`, `isReorderableCategory`) — never
+    test `effectiveType(m) === 'quantitative'` directly for measure-ness. `bin` makes a field a
+    discretized _dimension_ (mirrors Vega-Lite's `isDiscrete`); `aggregate` makes it a _measure_.
+    Reasoning over raw type is what made a histogram trip the two-measures→scatter nudge
+    (eng-council 2026-06-13; arch 10 §5). A new taste-heuristic warning should also be
+    high-precision: prefer structural/data-driven hints; lean on the intent front door + smart
+    defaults for positive guidance rather than enumerating bad combinations.
+
 ### Output
 
-15. **Summary**: respond with a summary of changes — choices made due to these instructions,
+16. **Summary**: respond with a summary of changes — choices made due to these instructions,
     choices where multiple approaches existed, and non-obvious architectural assumptions the
     user should know but might not spot in the diff. If the summary mentions an observation you
     chose not to fix (rule #8), confirm a `// TODO:` breadcrumb was placed at the code site.