fix(nitro): normalise uploaded bundles so meta.image matches the texture

An uploaded .nitro was written to disk byte-for-byte, so a bundle from a
third-party tool that ships a WebP member while still pointing
spritesheet.meta.image at a .png was accepted and stored as-is. The client
resolves the spritesheet through that pointer, so the result was a file
that validates fine and then renders nothing.

Re-write the bundle through createNitroBundle on import, which labels the
member from the actual bytes and repairs the pointer. No texture is
re-encoded, so the bytes stay identical, and the member keeps the base
name it arrived with so `chair*2` colour variants that share the `chair`
library are not renamed.

src/lib/services/upload-import.test.ts

@@ -84,8 +84,19 @@ vi.mock("@/lib/services/furni-import", () => ({
 	IMPORTED_PAGE_CAPTION_SAVE: "imported_furni",
 }));
 
+const nitroBuilderMock = vi.hoisted(() => ({
+	createNitroBundle: vi.fn((json: object) =>
+		Buffer.from(`rebuilt:${JSON.stringify(json)}`, "utf-8"),
+	),
+}));
+
 vi.mock("@/lib/services/swf/nitro-builder", () => ({
-	parseNitroBundle: vi.fn(() => ({ json: { xdim: 1, ydim: 1 } })),
+	parseNitroBundle: vi.fn(() => ({
+		json: { xdim: 1, ydim: 1 },
+		texture: Buffer.from("texture-bytes"),
+		textureFileName: "chair.png",
+	})),
+	createNitroBundle: nitroBuilderMock.createNitroBundle,
 }));
 
 import {
@@ -135,11 +146,19 @@ describe("uploadSingleFurni live asset mirrors", () => {
 		});
 
 		expect(result.ok).toBe(true);
+		// The bundle is re-written through the builder so `meta.image` can never
+		// disagree with the texture member, while the member keeps the name it
+		// arrived with (colour variants share a library name).
+		expect(nitroBuilderMock.createNitroBundle).toHaveBeenCalledWith(
+			{ xdim: 1, ydim: 1 },
+			Buffer.from("texture-bytes"),
+			"chair",
+		);
 		await expect(
 			fs.readFile(
 				getRuntimePath(assetTargets.mirrorDirs[0].nitroDir, "chair.nitro"),
 			),
-		).resolves.toEqual(nitroBuffer);
+		).resolves.toEqual(Buffer.from('rebuilt:{"xdim":1,"ydim":1}', "utf-8"));
 		await expect(
 			fs.readFile(
 				getRuntimePath(assetTargets.mirrorDirs[0].iconDir, "chair_icon.png"),