fix(extension): fall back to chunk when memory is whitespace-only

Graphite review: memory || chunk treated "   " as truthy and dropped a
valid chunk. Trim both fields before choosing.

apps/browser-extension/utils/hybrid-recall.eval.ts

@@ -92,12 +92,13 @@ export const HYBRID_RECALL_FIXTURES: HybridRecallFixture[] = [
 	},
 	{
 		id: "empty-and-whitespace-noise",
-		description: "Empty / whitespace hits must not invent prompt lines",
-		expectedTexts: ["Keep this fact"],
-		chunkOnlyTexts: [],
+		description:
+			"Whitespace-only memory must not block a valid chunk; blanks invent no lines",
+		expectedTexts: ["Keep this fact", "Important document text"],
+		chunkOnlyTexts: ["Important document text"],
 		results: [
 			{ memory: "Keep this fact" },
-			{ memory: "   " },
+			{ memory: "   ", chunk: "Important document text" },
 			{ chunk: "" },
 			{},
 		],

apps/browser-extension/utils/search-request.test.ts

@@ -37,6 +37,15 @@ describe("formatSearchHitText", () => {
 		)
 	})
 
+	it("falls back to chunk when memory is only whitespace", () => {
+		expect(
+			formatSearchHitText({
+				memory: "   ",
+				chunk: "Important document text",
+			}),
+		).toBe("Important document text")
+	})
+
 	it("returns null for empty hits", () => {
 		expect(formatSearchHitText({})).toBeNull()
 		expect(formatSearchHitText({ memory: "   " })).toBeNull()

apps/browser-extension/utils/search-request.ts

@@ -23,10 +23,10 @@ export function buildSearchMemoriesBody(
 
 /** Prefer extracted memory text; fall back to document chunk. */
 export function formatSearchHitText(hit: SearchHit): string | null {
-	const text = hit.memory || hit.chunk
-	if (typeof text !== "string") return null
-	const trimmed = text.trim()
-	return trimmed.length > 0 ? trimmed : null
+	const memory = typeof hit.memory === "string" ? hit.memory.trim() : ""
+	const chunk = typeof hit.chunk === "string" ? hit.chunk.trim() : ""
+	const text = memory || chunk
+	return text.length > 0 ? text : null
 }
 
 /** Numbered prompt lines for Included Memories; skips empty hits. */