An album whose folder cannot be made no longer stops the backup (closes #197)

Each album's folder, links and JSON are written inside one try. A failure
prints `FAILED album <name>: <reason>`, lists the album's ID in the result's
new `failedAlbums`, and so in `--json`, and makes `quak backup` exit 1. The
other albums and `failures.json` are still written.

An album whose folder would have another album's JSON name, ignoring case
(`x.json` beside `x`), gets its ID added. A folder or link name over 255
bytes is cut short between two characters by `shortenToBytes` in
`src/filename.ts`, and gets the ID; a folder name leaves room for `.json`.

Apart from its call to `uniqueNames`, the album loop is only indented into
the try.

Model: opus-5-5

test/cli/backup.test.ts

@@ -1703,6 +1703,31 @@ describe("backup album folders", () => {
         expect(readLedger(outDir).files["5"]).toMatchObject({ attempts: 2 });
     });
 
+    // The extension of this title is 303 bytes, so the ID cannot go before
+    // it, and the whole title is cut short with the ID at its end. The
+    // extension holds a "-", so the original is saved with `.bin`, a name
+    // that fits.
+    it("cuts a title short, extension and all, when its extension leaves no room for the ID", async () => {
+        const outDir = join(root, "backup");
+        const lib = libraryOf([
+            {
+                collection: collection(10, "Trip"),
+                files: [file(1, 10, `a.${"L".repeat(300)}-x`)],
+            },
+        ]);
+
+        const result = await runBackup(lib, { downloadDirectory: outDir });
+
+        const link = `a.${"L".repeat(249)} (1)`;
+        expect(Buffer.byteLength(link)).toBe(255);
+        expect(result.failed).toBe(0);
+        expect(tree(outDir)).toEqual([
+            "Trip/",
+            `Trip/${link} -> ${linkTo("1.bin")}`,
+            "Trip.json",
+        ]);
+    });
+
     // The user has put a file in collections/ with the name of the album
     // Trip's folder, so the folder cannot be made.
     it("goes on to the next album when an album's folder cannot be made, and lists it as failed", async () => {