A recording under 1 KB has no picture to take: its thumbnail job fails for good (404), not as retryable (#282)

ddiff --git a/server/jobs/thumbnail.js b/server/jobs/thumbnail.js
iindex 27e2c54..e341f40 100644
---- a/server/jobs/thumbnail.js
++++ b/server/jobs/thumbnail.js
@@@ -73,6 +73,9 @@ async function run(job) {
          let size = 0;
          try { size = require('fs').statSync(source.value).size; } catch { size = 0; }
          if (!size) throw new JobError('media_unavailable', 'The media file is empty (0 bytes)', { permanent: true, status: 404 });
++        // A few hundred bytes hold a container header and no frame (VOD 1803: 526 bytes for "51 seconds", health "ok"):
++        // ffmpeg fails every time, and a retryable failure had every page that shows it ask again (2026-11-02).
++        if (size < TOO_SMALL_FOR_A_FRAME) throw new JobError('media_unavailable', `The media file is too small to hold a picture (${size} bytes)`, { permanent: true, status: 404 });
      }
      // An audio-only source (a browser broadcast with no camera, Media#240) has no frame to take. Its picture is the
      // streamer's avatar card, made once here and stored like any thumbnail, and the row is marked audio_only. This used
@@@ -96,6 +99,9 @@ async function run(job) {
      return { url, kind, id };
  }
  
++// Under 1 KB is a container header at most, with no frame in it: no picture to take.
++const TOO_SMALL_FOR_A_FRAME = 1024;
++
  module.exports = {
      spec: { lane: 'light', maxAttempts: 2, timeoutMs: 2 * 60 * 1000, needsObject: false, backoffS: () => 20, validate, run },
      targetOf,
ddiff --git a/test/jobs.test.js b/test/jobs.test.js
iindex ee6a032..9a3beee 100644
---- a/test/jobs.test.js
++++ b/test/jobs.test.js
@@@ -246,7 +246,8 @@ const http = require('http');
          const thumbs = require('../server/thumbnails/thumbnail-service');
          let gens = 0;
          thumbs.generateVodThumbnail = async (id) => { gens++; await sleep(150); await db.run('UPDATE vods SET thumbnail_url = ? WHERE id = ?', [`/t/vod-${id}-1.jpg`, id]); return `/t/vod-${id}-1.jpg`; };
--        fs.writeFileSync(path.join(process.env.VOD_PATH, 'rec-1.webm'), 'not really a video');
++        // A stand-in recording of a real size: under 1 KB a file has no picture to take and the job fails for good.
++        fs.writeFileSync(path.join(process.env.VOD_PATH, 'rec-1.webm'), Buffer.alloc(4096, 'not really a video '));
          await conn.prepare("INSERT INTO vods (id, app_id, user_id, title, file_path, is_public, duration_seconds) OVERRIDING SYSTEM VALUE VALUES (1, 'live', 5, 'A', ?, 1, 60) RETURNING id").run(path.join(process.env.VOD_PATH, 'rec-1.webm'));
          await conn.prepare("INSERT INTO vods (id, app_id, user_id, title, file_path, is_public, duration_seconds) OVERRIDING SYSTEM VALUE VALUES (2, 'live', 5, 'B', ?, 1, 60) RETURNING id").run(path.join(process.env.VOD_PATH, 'gone.webm'));
          await require('../server/objects/model').sync('vod', 1);
ddiff --git a/test/thumbnail-unavailable.test.js b/test/thumbnail-unavailable.test.js
iindex e113c7b..fe092ea 100644
---- a/test/thumbnail-unavailable.test.js
++++ b/test/thumbnail-unavailable.test.js
@@@ -31,6 +31,8 @@ const express = require('express');
      const marked = await insVod(path.join(V, 'zero-marked.mp4'), 'zero_byte');          // as on production
      const unscanned = await insVod(path.join(V, 'zero-unscanned.mp4'), 'unknown');      // empty, not scanned yet
      const missing = await insVod(path.join(V, 'gone.mp4'), 'ok');                        // no file, not offloaded
++    fs.writeFileSync(path.join(V, 'tiny.mp4'), Buffer.alloc(526, 1));
++    const tiny = await insVod(path.join(V, 'tiny.mp4'), 'ok');                           // 526 bytes, health ok (VOD 1803)
  
      const app = express();
      app.use(express.json());
@@@ -45,7 +47,7 @@ const express = require('express');
  
      (async () => {
          await new Promise((r) => (server.listening ? r() : server.once('listening', r)));
--        for (const id of [marked, unscanned, missing]) {
++        for (const id of [marked, unscanned, missing, tiny]) {
              const t0 = Date.now();
              const r = await post(`/api/v1/live/thumbnails/vod/${id}`);
              assert.strictEqual(r.status, 404, `vod ${id}: ${JSON.stringify(r.body)}`);