Skip thumbnail repairs the server always refuses (closes #109)

The server accepts a new thumbnail only from the file's owner and only when
it is no larger than the thumbnail size it records. Both thumbnail helpers
now skip files another account owns without fetching them. The fixer skips
a file whose recorded thumbnail size is 0 or unknown before downloading it,
and otherwise tries smaller encodings until the encrypted thumbnail fits,
skipping the file if none does.

Model: opus-5-5

src/cli-commands.ts

@@ -495,7 +495,7 @@ export const fixMissingThumbnailsCommand = async (
             ctx.stderr.write(`  Skipped: ${skipped}\n`);
             ctx.stderr.write(`  Failed:  ${failed}\n`);
             if (skipped > 0) {
-                ctx.stderr.write("\nSkipped (unsupported format):\n");
+                ctx.stderr.write("\nSkipped:\n");
                 for (const r of results.filter((r) => r.status === "skipped")) {
                     ctx.stderr.write(
                         `  ${r.fileID}\t${r.title}\t${r.reason}\n`,