test(benchmark): print a readable summary table

Print the calibration and a Markdown table with one aligned row per
scenario as soon as it finishes: both planning times, mean, budget, ratio,
multiplier, outcome, placements, determinism and budget status. Write
directly to stdout so Vitest adds no per-line headers. The complete TSV
report still follows the table.

Refs #281, #285

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/benchmark/leave-planner-benchmark.ts

@@ -277,12 +277,12 @@ async function measureRepetition(
 	}
 }
 
-export const BENCHMARK_REPORT_HEADER =
-	'scenario\trepetition\tpreparation_ms\tplanning_ms\twall_ms\toutcome\tlast_stage\tplacements\tdeterministic\tmax_ui_delay_ms\tplanning_work_ms\tpeak_main_thread_heap_bytes';
-
-export function benchmarkReportRows(measurements: BenchmarkMeasurement[]): string {
-	return measurements
-		.map((item) =>
+export function benchmarkReport(measurements: BenchmarkMeasurement[]): string {
+	const header =
+		'scenario\trepetition\tpreparation_ms\tplanning_ms\twall_ms\toutcome\tlast_stage\tplacements\tdeterministic\tmax_ui_delay_ms\tplanning_work_ms\tpeak_main_thread_heap_bytes';
+	return [
+		header,
+		...measurements.map((item) =>
 			[
 				item.scenario,
 				item.repetition,
@@ -297,15 +297,8 @@ export function benchmarkReportRows(measurements: BenchmarkMeasurement[]): strin
 				item.planningWorkMs?.toFixed(1) ?? '',
 				item.peakMainThreadHeapBytes ?? '',
 			].join('\t'),
-		)
-		.join('\n');
-}
-
-export function benchmarkReport(measurements: BenchmarkMeasurement[]): string {
-	// Empty input yields the header alone, with no trailing newline.
-	return measurements.length
-		? [BENCHMARK_REPORT_HEADER, benchmarkReportRows(measurements)].join('\n')
-		: BENCHMARK_REPORT_HEADER;
+		),
+	].join('\n');
 }
 
 // Measured on the development machine (ratio to the frozen two-years run), tightened by #286.
@@ -330,7 +323,7 @@ export function budgetViolations(
 		byScenario.set(scenario, [...(byScenario.get(scenario) ?? []), planningMs]);
 	const violations: string[] = [];
 	for (const [scenario, times] of byScenario) {
-		const mean = times.reduce((sum, value) => sum + value, 0) / times.length;
+		const mean = average(times);
 		const multiplier = multipliers[scenario];
 		if (multiplier === undefined) {
 			violations.push(`${scenario}: no budget multiplier defined`);
@@ -344,3 +337,65 @@ export function budgetViolations(
 	}
 	return violations;
 }
+
+function average(values: number[]): number {
+	return values.reduce((sum, value) => sum + value, 0) / values.length;
+}
+
+// Fixed widths keep rows printed as each scenario finishes aligned with the header.
+const SUMMARY_COLUMNS: [title: string, width: number, alignRight: boolean][] = [
+	['Scenario', 27, false],
+	['Planning (runs)', 17, true],
+	['Mean', 9, true],
+	['Budget', 9, true],
+	['Ratio', 6, true],
+	['Limit', 6, true],
+	['Outcome', 16, false],
+	['Placements', 10, true],
+	['Deterministic', 13, false],
+	['Status', 9, false],
+];
+
+function summaryLine(cells: string[]): string {
+	return `| ${cells
+		.map((cell, index) => {
+			const [, width, alignRight] = SUMMARY_COLUMNS[index];
+			return alignRight ? cell.padStart(width) : cell.padEnd(width);
+		})
+		.join(' | ')} |`;
+}
+
+/** Markdown table header for {@link benchmarkSummaryRow}. */
+export function benchmarkSummaryHeader(): string {
+	return [
+		summaryLine(SUMMARY_COLUMNS.map(([title]) => title)),
+		`|${SUMMARY_COLUMNS.map(([, width, alignRight]) => (alignRight ? `${'-'.repeat(width + 1)}:` : `:${'-'.repeat(width + 1)}`)).join('|')}|`,
+	].join('\n');
+}
+
+/** One aligned table row for one scenario's measured repetitions, judged like {@link budgetViolations}. */
+export function benchmarkSummaryRow(
+	scenarioMeasurements: BenchmarkMeasurement[],
+	calibrationMs: number,
+	multipliers: Record<string, number> = BENCHMARK_BUDGET_MULTIPLIERS,
+): string {
+	const [first] = scenarioMeasurements;
+	const seconds = (ms: number) => (ms / 1000).toFixed(2);
+	const mean = average(scenarioMeasurements.map(({ planningMs }) => planningMs));
+	const multiplier = multipliers[first.scenario];
+	const budget = multiplier === undefined ? undefined : multiplier * calibrationMs;
+	return summaryLine([
+		first.scenario,
+		`${scenarioMeasurements.map(({ planningMs }) => seconds(planningMs)).join(' / ')} s`,
+		`${seconds(mean)} s`,
+		budget === undefined ? '-' : `${seconds(budget)} s`,
+		(mean / calibrationMs).toFixed(2),
+		multiplier === undefined ? '-' : String(multiplier),
+		first.lastCompletedStage ? `${first.outcome} (${first.lastCompletedStage})` : first.outcome,
+		String(first.placements),
+		scenarioMeasurements.slice(1).every(({ deterministic }) => deterministic === 'yes')
+			? 'yes'
+			: 'no',
+		budget === undefined ? 'no budget' : mean > budget ? 'OVER' : 'ok',
+	]);
+}