A network failure is printed and recorded with its reason (closes #196)

Node's `fetch` rejects every failure below HTTP as `fetch failed` and puts
the reason on `cause`. `describeError` in `src/errors.ts` gives the message
followed by the messages on the cause chain, and for an `AggregateError`,
which Node gives when every address of a host fails, the message of each
address. `run` prints it, and the backup logs and records it. `classify`
reads that text and calls a failure transient when `hasTransportCode`, now
exported by `src/retry.ts`, finds a transport errno on the chain. A failed
ML data fetch keeps its error as the cause. The bounded walk along the
chain moved from `src/retry.ts` to `src/errors.ts`.

A truncated download's message leaves the authentication failure to its
cause.

Model: opus-5-5

test/cli/run.test.ts

@@ -48,6 +48,78 @@ describe("run", () => {
         );
     });
 
+    // Node's `fetch` rejects every failure below HTTP with a TypeError that
+    // says only "fetch failed", and hangs the reason, with its errno, off
+    // `cause`. The printed line carries the reason, so a cron log tells a
+    // refused connection from a name that did not resolve.
+    it("prints the reason a fetch failed, from the error's cause", async () => {
+        const refused = new TypeError("fetch failed", {
+            cause: Object.assign(
+                new Error("connect ECONNREFUSED 1.2.3.4:443"),
+                { code: "ECONNREFUSED" },
+            ),
+        });
+        const result = await runToExit(Promise.reject(refused));
+        expect(result).toEqual({
+            code: 1,
+            stdout: "",
+            stderr: "quak: fetch failed: connect ECONNREFUSED 1.2.3.4:443\n",
+        });
+    });
+
+    // When the host has several addresses and every one refuses, Node's
+    // `fetch` gives as the cause an AggregateError with an empty message and
+    // one error per address. The printed line gives each address's reason.
+    it("prints the reason for each address a fetch could not reach", async () => {
+        const refusedAt = (address: string): Error =>
+            Object.assign(new Error(`connect ECONNREFUSED ${address}`), {
+                code: "ECONNREFUSED",
+            });
+        const refused = new TypeError("fetch failed", {
+            cause: Object.assign(
+                new AggregateError([
+                    refusedAt("2001:db8::1:443"),
+                    refusedAt("1.2.3.4:443"),
+                ]),
+                { code: "ECONNREFUSED" },
+            ),
+        });
+        const result = await runToExit(Promise.reject(refused));
+        expect(result).toEqual({
+            code: 1,
+            stdout: "",
+            stderr: "quak: fetch failed: connect ECONNREFUSED 2001:db8::1:443, connect ECONNREFUSED 1.2.3.4:443\n",
+        });
+    });
+
+    // An error that already quotes its cause's message is printed as it is.
+    it("does not print a cause's message twice", async () => {
+        const reset = new Error("read ECONNRESET");
+        const wrapped = new Error(`download: file 7: ${reset.message}`, {
+            cause: reset,
+        });
+        const result = await runToExit(Promise.reject(wrapped));
+        expect(result.stderr).toBe("quak: download: file 7: read ECONNRESET\n");
+    });
+
+    // OpenSSL ends its message for a failed TLS connection, such as one to a
+    // server that answers in plain HTTP, with a newline. The printed line is
+    // still one line.
+    it("prints a cause's message without the white space around it", async () => {
+        const wrongVersion = new TypeError("fetch failed", {
+            cause: Object.assign(
+                new Error(
+                    "C0B73A55A47F0000:error:0A00010B:SSL routines:ssl3_get_record:wrong version number:../deps/openssl/openssl/ssl/record/ssl3_record.c:354:\n",
+                ),
+                { code: "ERR_SSL_WRONG_VERSION_NUMBER" },
+            ),
+        });
+        const result = await runToExit(Promise.reject(wrongVersion));
+        expect(result.stderr).toBe(
+            "quak: fetch failed: C0B73A55A47F0000:error:0A00010B:SSL routines:ssl3_get_record:wrong version number:../deps/openssl/openssl/ssl/record/ssl3_record.c:354:\n",
+        );
+    });
+
     it("prints a thrown value that is not an Error", async () => {
         const result = await runToExit(Promise.reject("offline"));
         expect(result).toEqual({
@@ -57,6 +129,14 @@ describe("run", () => {
         });
     });
 
+    // A cause that is not an Error, such as a thrown string, is printed as a
+    // thrown value that is not an Error is.
+    it("prints a cause that is not an Error", async () => {
+        const wrapped = new Error("ML data", { cause: "offline" });
+        const result = await runToExit(Promise.reject(wrapped));
+        expect(result.stderr).toBe("quak: ML data: offline\n");
+    });
+
     it("on a 401 from the server says to run quak login, on one line, and exits 3", async () => {
         const result = await runToExit(
             Promise.reject(new ApiError("unauthorized", 401)),