test(telemetry): tighten OTLP writer test coverage

Addresses R2 review feedback on PR #961:
- records: assert the Math.max(0, ...) negative-counter clamp directly
  (existing Infinity case only exercised the isFinite guard).
- records: cover the result="error" + error object combination so a
  regression on the spread of error.message is caught.
- envelope: also assert stream.destroyed on the stream.end failure path
  (matches the sibling suffix-write test).
- metrics: swap %p (not a Vitest format specifier) for %s in it.each
  titles so boolean rows render.

Author: EhabY

test/unit/telemetry/export/metrics.test.ts

@@ -12,7 +12,7 @@ describe("isMetricEvent", () => {
 		["ssh.network.sampled", true],
 		["log.something", false],
 		["remote.setup.workspace_ready", false],
-	])("returns %s for %p", (name, expected) => {
+	])("returns %s for %s", (name, expected) => {
 		expect(isMetricEvent(makeEvent({ eventName: name }))).toBe(expected);
 	});
 });

test/unit/telemetry/export/writers/otlp/envelope.test.ts

@@ -101,12 +101,13 @@ describe("openEnvelopeFile", () => {
 		expect(stream.destroyed).toBe(1);
 	});
 
-	it("wraps stream.end failures with the file path", async () => {
+	it("wraps stream.end failures with the file path and releases the fd", async () => {
 		const env = await openEnvelopeFile("/foo.json", "[", "]");
 		stream.endFailMsg = "stream gone";
 		await expect(env.close()).rejects.toThrow(
 			"Failed to close /foo.json: stream gone",
 		);
+		expect(stream.destroyed).toBe(1);
 	});
 
 	it("rejects subsequent writes after the stream emits 'error'", async () => {

test/unit/telemetry/export/writers/otlp/records.test.ts

@@ -140,6 +140,10 @@ describe("spanRecord", () => {
 	it.each([
 		[{ properties: { result: "success" } }, { code: 1 }],
 		[{ properties: { result: "error" } }, { code: 2 }],
+		[
+			{ properties: { result: "error" }, error: { message: "boom" } },
+			{ code: 2, message: "boom" },
+		],
 		[{ error: { message: "boom" } }, { code: 2, message: "boom" }],
 		[{}, { code: 0 }],
 	])("maps span status: %j -> %j", (overrides, expected) => {
@@ -336,6 +340,24 @@ describe("metricRecords", () => {
 		]);
 	});
 
+	it("clamps negative counter deltas so the cumulative total never decreases", () => {
+		// Without Math.max(0, ...) a negative delta would shrink the total; backends
+		// read a decreasing monotonic sum as a counter reset.
+		const state = newCumulativeState();
+		metricRecords(
+			makeEvent({ eventName: "http.requests" }),
+			{ windowSeconds: 60, measurements: [counter("count.2xx", 5)] },
+			state,
+		);
+		const [record] = metricRecords(
+			makeEvent({ eventName: "http.requests" }),
+			{ windowSeconds: 60, measurements: [counter("count.2xx", -3)] },
+			state,
+		);
+
+		expect(record.sum!.dataPoints[0].asInt).toBe("5");
+	});
+
 	it("treats windowSeconds=0 as a zero-width window", () => {
 		const [record] = metricRecords(
 			makeEvent({ eventName: "http.requests" }),