fix(logs): deep-review round 3 — a failure nobody could record is one scrubbed line

- The download and edit failure lines go back after their DB write: a job the
  write could not fail is not a failed job, and the worker's child_exit line
  already says it failed.
- The download child's runner is the last stop before Python's hook: an
  escaping exception is one download.child.failed line with its chain scrubbed,
  then exit 1, instead of a raw stderr traceback carrying the URL.
- A crash the database will not record carries its stack once, and the
  fail-write line has an event code.
- The job's own generic-extractor name is taken out as a literal (formats.hiding),
  so brackets and colons in a direct link's file name no longer leak; the
  pattern stays as the fallback. `Downloading just the video <id>` is covered.
- Tests: scrubbed_stack's cause, suppress, unprintable and text-format paths,
  the image steps' failure kinds, the watchdog error through the real
  _fail_running, exact poster/storyboard messages, ffmpeg skip marker.

backend/tests/test_download_failure_catalog.py

@@ -125,9 +125,9 @@ def test_the_download_child_knows_the_cookie_went_with_it(db, monkeypatch, tmp_p
     assert (job.error_code, job.error_detail) == ("login_required", "facebook.cookie_rejected")
 
 
-def test_the_failure_line_goes_out_even_when_its_write_fails(db, monkeypatch, tmp_path):
-    """The database is often what failed; the write of the failure then fails too, and the line
-    that says so must not go down with it."""
+def test_a_failure_the_database_would_not_record_is_not_claimed(db, monkeypatch, tmp_path):
+    """The job is still `running`: the runner reports this with the write's error, and the worker
+    fails the job. A `download.job.failed` here as well would be a second line, and a false one."""
     u = _user(db, "fb-dbdown@example.com")
     a, j = _asset_and_job(db, u, sig="dbdown", asset_status="downloading", job_status="running")
     _fail_the_child(monkeypatch, tmp_path, cookie=False)
@@ -141,7 +141,7 @@ def test_the_failure_line_goes_out_even_when_its_write_fails(db, monkeypatch, tm
 
     with pytest.raises(ConnectionError):
         pipeline._download(j.id, a.id, "url", _REEL, {}, u.id)
-    assert said == [j.id]
+    assert said == []
 
 
 def test_a_job_meeting_a_failed_shared_asset_gets_the_same_explanation(db):