[Agent Builder] Add chart type specific config prompt rules to visualization tool (elastic#260269)

## Summary

Resolves elastic#259508

Add support for per-chart type configuration rules that are injected
into the config generation prompt. This allows chart types to define
specific constrains - e.g., gauge charts should omit min/max bounds by
default (included in this PR as well).

Author: rbrtj

x-pack/platform/packages/shared/agent-builder/agent-builder-genai-utils/tools/visualization/chart_type_guidance.ts

@@ -5,6 +5,7 @@
  * 2.0.
  */
 
+import type { SupportedChartType } from '@kbn/agent-builder-common/tools/tool_result';
 import { chartTypeRegistry } from './chart_type_registry';
 
 export const getChartTypeSelectionPromptContent = () =>
@@ -18,3 +19,16 @@ export const getChartTypeSelectionPromptContent = () =>
     ...Object.entries(chartTypeRegistry).map(([, { guidance }]) => `- ${guidance.guideline}`),
     "- Consider the user's intent and the nature of the data being visualized",
   ].join('\n');
+
+export const getChartTypeConfigPromptContent = (chartType: SupportedChartType) => {
+  const configPromptRules = chartTypeRegistry[chartType].configPromptRules;
+
+  if (!configPromptRules?.length) {
+    return '';
+  }
+
+  return [
+    `CHART-SPECIFIC RULES FOR ${chartType.toUpperCase()}:`,
+    ...configPromptRules.map((rule) => `- ${rule}`),
+  ].join('\n');
+};

x-pack/platform/packages/shared/agent-builder/agent-builder-genai-utils/tools/visualization/chart_type_registry.ts

@@ -21,6 +21,7 @@ import { mosaicStateSchemaESQL } from '@kbn/lens-embeddable-utils/config_builder
 interface ChartTypeRegistryEntry {
   schema: { validate: (config: unknown) => any; getSchema: () => any };
   guidance: { description: string; guideline: string };
+  configPromptRules?: string[];
 }
 
 /**
@@ -34,7 +35,7 @@ interface ChartTypeRegistryEntry {
  * TypeScript enforces exhaustiveness via `satisfies Record<SupportedChartType, ...>` —
  * a missing entry is a compile error.
  */
-export const chartTypeRegistry = {
+export const chartTypeRegistry: Record<SupportedChartType, ChartTypeRegistryEntry> = {
   [SupportedChartType.Metric]: {
     schema: esqlMetricState,
     guidance: {
@@ -52,6 +53,11 @@ export const chartTypeRegistry = {
       guideline:
         "Choose 'gauge' when showing a value within a range, progress toward a goal, or performance against min/max thresholds",
     },
+    configPromptRules: [
+      "Always omit the optional 'min' and 'max' fields from the final configuration.",
+      'Do not infer, synthesize, or backfill gauge bounds from the ES|QL results or the user request.',
+      'Only include goal/target-related fields when the user explicitly asks for a goal or threshold.',
+    ],
   },
   [SupportedChartType.XY]: {
     schema: xyStateSchemaESQL,
@@ -134,7 +140,7 @@ export const chartTypeRegistry = {
         "Choose 'mosaic' when visualizing the joint distribution of two categorical dimensions",
     },
   },
-} satisfies Record<SupportedChartType, ChartTypeRegistryEntry>;
+};
 
 export type ChartTypeRegistry = typeof chartTypeRegistry;
 

x-pack/platform/packages/shared/agent-builder/agent-builder-genai-utils/tools/visualization/prompts.ts

@@ -7,6 +7,7 @@
 
 import type { BaseMessageLike } from '@langchain/core/messages';
 import type { SupportedChartType } from '@kbn/agent-builder-common/tools/tool_result';
+import { getChartTypeConfigPromptContent } from './chart_type_guidance';
 
 export const createGenerateConfigPrompt = ({
   nlQuery,
@@ -25,6 +26,8 @@ export const createGenerateConfigPrompt = ({
   additionalChartConfigInstructions?: string;
   additionalContext?: string;
 }): BaseMessageLike[] => {
+  const chartTypeConfigPromptContent = getChartTypeConfigPromptContent(chartType);
+
   return [
     [
       'system',
@@ -65,6 +68,8 @@ NUMBER FORMAT RULES:
 - When column names or the user query hint at a unit (e.g. "cpu", "percent", "bytes_in", "disk_used", "latency_ms"), infer the correct format even if the user did not explicitly ask for it.
 - Do NOT apply a format when the metric is a plain count, rate, or when the unit is ambiguous.
 
+${chartTypeConfigPromptContent ? `${chartTypeConfigPromptContent}` : ''}
+
 ${additionalChartConfigInstructions ?? ''}
 
 Your task is to generate a ${chartType} visualization configuration based on the following information:

x-pack/platform/plugins/shared/dashboard_agent/server/skills/grid_layout_prompt.ts

@@ -15,10 +15,13 @@ Every \`add_panels_from_attachments\` item requires \`grid: { x, y, w, h }\`. Th
 
 Use these sizes — **do not make metric or gauge panels full-width**:
 
-- **Metric / Gauge** → \`w: 8–16, h: 5–6\`. These are single-number panels — keep them **small**. Fit 3–6 per row.
+- **Metric** → \`w: 8–16, h: 5–6\`. These are single-number panels — keep them **small**. Fit 3–6 per row.
   - 6 metrics in a row: each \`w: 8, h: 5\`
   - 4 metrics in a row: each \`w: 12, h: 5\`
   - 3 metrics in a row: each \`w: 16, h: 6\`
+- **Gauge** → \`w: 12–16, h: 9–12\`. Gauges need extra vertical space for the dial, but should still stay compact. Fit 3–4 per row.
+  - 4 gauges in a row: each \`w: 12, h: 9\`
+  - 3 gauges in a row: each \`w: 16, h: 10–12\`
 - **XY (line / area / bar)** → \`w: 24, h: 10–12\` (half-width) or \`w: 48, h: 14–16\` (full-width for primary time series).
 - **Heatmap** → \`w: 24–48, h: 10–12\`. Needs height for the color matrix.
 - **Tagcloud** → \`w: 24, h: 8–10\`.