test(summary-helpers): add regression tests for extractSliceExecutionExcerpt

Verifies the function handles null/undefined content gracefully and
correctly extracts goal, demo, verification, and observability sections
from slice plan content. Addresses sf-mozutl5d-ei3ec6 by ensuring the
function is importable and behaves correctly end-to-end.

src/resources/extensions/sf/tests/summary-helpers.test.mjs

@@ -0,0 +1,72 @@
+import assert from "node:assert/strict";
+import { test } from "vitest";
+import {
+	extractSliceExecutionExcerpt,
+} from "../summary-helpers.js";
+
+test("extractSliceExecutionExcerpt when content is null returns fallback", () => {
+	const result = extractSliceExecutionExcerpt(null, "S01/PLAN.md");
+	assert.ok(result.includes("## Slice Plan Excerpt"));
+	assert.ok(result.includes("Slice plan not found"));
+	assert.ok(result.includes("S01/PLAN.md"));
+});
+
+test("extractSliceExecutionExcerpt when content is undefined returns fallback", () => {
+	const result = extractSliceExecutionExcerpt(undefined, "S02/PLAN.md");
+	assert.ok(result.includes("## Slice Plan Excerpt"));
+	assert.ok(result.includes("Slice plan not found"));
+	assert.ok(result.includes("S02/PLAN.md"));
+});
+
+test("extractSliceExecutionExcerpt extracts goal and demo lines", () => {
+	const content = [
+		"# Slice Plan",
+		"",
+		"**Goal:** This slice delivers X",
+		"",
+		"**Demo:** After this, you can Y",
+		"",
+		"## Verification",
+		"Run npm test",
+	].join("\n");
+
+	const result = extractSliceExecutionExcerpt(content, "S01/PLAN.md");
+	assert.ok(result.includes("**Goal:** This slice delivers X"));
+	assert.ok(result.includes("**Demo:** After this, you can Y"));
+	assert.ok(result.includes("Source: `S01/PLAN.md`"));
+});
+
+test("extractSliceExecutionExcerpt extracts verification section", () => {
+	const content = [
+		"# Slice Plan",
+		"",
+		"**Goal:** Test goal",
+		"",
+		"## Verification",
+		"Run the integration suite",
+		"Check exit code is 0",
+		"",
+		"## Observability / Diagnostics",
+		"Metrics at /metrics",
+	].join("\n");
+
+	const result = extractSliceExecutionExcerpt(content, "S01/PLAN.md");
+	assert.ok(result.includes("### Slice Verification"));
+	assert.ok(result.includes("Run the integration suite"));
+	assert.ok(result.includes("Check exit code is 0"));
+	assert.ok(result.includes("### Slice Observability / Diagnostics"));
+	assert.ok(result.includes("Metrics at /metrics"));
+});
+
+test("extractSliceExecutionExcerpt omits missing sections gracefully", () => {
+	const content = [
+		"# Slice Plan",
+		"",
+		"**Goal:** Minimal slice",
+	].join("\n");
+
+	const result = extractSliceExecutionExcerpt(content, "S01/PLAN.md");
+	assert.ok(result.includes("**Goal:** Minimal slice"));
+	assert.ok(!result.includes("### Slice Verification"));
+	assert.ok(!result.includes("### Slice Observability"));
+});