Add scenario-modeler-server example

Demo MCP App for SaaS financial planning with:
- Interactive sliders for MRR, growth, churn, margin, and costs
- 12-month projection charts (MRR, Gross Profit, Net Profit)
- 5 pre-built scenario templates (Bootstrapped, VC Rocketship, etc.)
- Template comparison overlay for strategy analysis
- Light/dark theme support

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

examples/scenario-modeler-server/src/lib/calculations.ts

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+import type {
+  ScenarioInputs,
+  MonthlyProjection,
+  ScenarioSummary,
+} from "../types.ts";
+
+export function calculateProjections(
+  inputs: ScenarioInputs,
+): MonthlyProjection[] {
+  const {
+    startingMRR,
+    monthlyGrowthRate,
+    monthlyChurnRate,
+    grossMargin,
+    fixedCosts,
+  } = inputs;
+
+  // Net growth rate (can be negative if churn > growth)
+  const netGrowthRate = (monthlyGrowthRate - monthlyChurnRate) / 100;
+
+  const projections: MonthlyProjection[] = [];
+  let cumulativeRevenue = 0;
+
+  for (let month = 1; month <= 12; month++) {
+    // MRR with compound growth
+    const mrr = startingMRR * Math.pow(1 + netGrowthRate, month);
+
+    // Profit calculations
+    const grossProfit = mrr * (grossMargin / 100);
+    const netProfit = grossProfit - fixedCosts;
+
+    // Cumulative revenue
+    cumulativeRevenue += mrr;
+
+    projections.push({
+      month,
+      mrr,
+      grossProfit,
+      netProfit,
+      cumulativeRevenue,
+    });
+  }
+
+  return projections;
+}
+
+export function calculateSummary(
+  projections: MonthlyProjection[],
+  inputs: ScenarioInputs,
+): ScenarioSummary {
+  const endingMRR = projections[11].mrr;
+  const arr = endingMRR * 12;
+  const totalRevenue = projections.reduce((sum, p) => sum + p.mrr, 0);
+  const totalProfit = projections.reduce((sum, p) => sum + p.netProfit, 0);
+  const mrrGrowthPct =
+    ((endingMRR - inputs.startingMRR) / inputs.startingMRR) * 100;
+  const avgMargin = (totalProfit / totalRevenue) * 100;
+
+  // Find first month where netProfit >= 0
+  const breakEvenProjection = projections.find((p) => p.netProfit >= 0);
+  const breakEvenMonth = breakEvenProjection?.month ?? null;
+
+  return {
+    endingMRR,
+    arr,
+    totalRevenue,
+    totalProfit,
+    mrrGrowthPct,
+    avgMargin,
+    breakEvenMonth,
+  };
+}

examples/scenario-modeler-server/src/lib/formatters.ts

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+/**
+ * Format a number as currency with abbreviated suffixes.
+ * Examples: $50K, $1.2M, -$30K
+ */
+export function formatCurrency(value: number): string {
+  const absValue = Math.abs(value);
+  const sign = value < 0 ? "-" : "";
+
+  if (absValue >= 1_000_000) {
+    const formatted = (absValue / 1_000_000).toFixed(
+      absValue >= 10_000_000 ? 1 : 2,
+    );
+    // Remove trailing zeros after decimal
+    const cleaned = formatted.replace(/\.?0+$/, "");
+    return `${sign}$${cleaned}M`;
+  }
+
+  if (absValue >= 1_000) {
+    const formatted = (absValue / 1_000).toFixed(absValue >= 100_000 ? 0 : 1);
+    const cleaned = formatted.replace(/\.?0+$/, "");
+    return `${sign}$${cleaned}K`;
+  }
+
+  return `${sign}$${Math.round(absValue)}`;
+}
+
+/**
+ * Format a number as a percentage.
+ * Examples: 5%, -2.5%, +12%
+ */
+export function formatPercent(value: number, showSign = false): string {
+  const sign = showSign && value > 0 ? "+" : "";
+  return `${sign}${value.toFixed(1).replace(/\.0$/, "")}%`;
+}
+
+/**
+ * Format currency for slider display (always show K suffix for consistency).
+ */
+export function formatCurrencySlider(value: number): string {
+  if (value >= 1_000) {
+    return `$${(value / 1_000).toFixed(0)}K`;
+  }
+  return `$${value}`;
+}