test(fit): adapt single-point GPX case to the parser's <2-point drop

CI "Unit Tests" (full monorepo) caught that @trails-cool/fit's round-trip
fixture loop included single-point.gpx, which now parses to zero track
points (the parser drops <2-point segments), so gpxToFitCourse correctly
throws its zero-points guard. Drop single-point.gpx from the round-trip
loop and cover the degenerate case explicitly: a lone point → zero points
→ refused.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/fit/src/gpx-to-fit-course.test.ts

@@ -33,7 +33,11 @@ function decode(bytes: Uint8Array): Promise<ParsedFit> {
   });
 }
 
-const FIXTURES = ["short-flat.gpx", "alpine.gpx", "multi-day.gpx", "single-point.gpx"] as const;
+// single-point.gpx is intentionally excluded from the round-trip loop: the
+// GPX parser now drops segments left with fewer than 2 points
+// (gpx-parser-robustness), so a lone point yields zero track points and
+// can't round-trip. That degenerate case is covered on its own below.
+const FIXTURES = ["short-flat.gpx", "alpine.gpx", "multi-day.gpx"] as const;
 
 describe("gpxToFitCourse", () => {
   for (const fixture of FIXTURES) {
@@ -67,6 +71,14 @@ describe("gpxToFitCourse", () => {
     await expect(gpxToFitCourse({ gpx, name: "Empty" })).rejects.toThrow(/zero track points/);
   });
 
+  it("drops a single-point GPX to zero points, so it is refused", async () => {
+    // The parser discards <2-point segments (gpx-parser-robustness), so a
+    // lone point can't form a FIT course — the zero-points guard fires.
+    const gpx = await loadFixture("single-point.gpx");
+    expect((await parseGpxAsync(gpx)).tracks.flat()).toHaveLength(0);
+    await expect(gpxToFitCourse({ gpx, name: "Single" })).rejects.toThrow(/zero track points/);
+  });
+
   it("advertises position+distance course capabilities (not time-only)", async () => {
     const gpx = await loadFixture("short-flat.gpx");
     const bytes = await gpxToFitCourse({ gpx, name: "Caps", sport: "cycling" });