fix(logs): deep-review round 1 — say each failure once, and scrub it everywhere

- yt-dlp's text is scrubbed wherever it is logged, not only in the adapter:
  `formats.log_safe` takes out the URL, the `[extractor] <id>:` prefix and
  file paths, and the job-failed, refused, edit-failed and backfill lines use
  it. Done lines log the asset id, not the title-built path. The PII contract
  now bans `rel`/`rel_path`/`title`.
- A traceback goes with a download/edit failure only when it is our own code
  failing; for yt-dlp's DownloadError, our RuntimeErrors and OSErrors its foot
  is the unscrubbed message.
- yt-dlp's `error` maps to WARNING: it fires on attempts the fallback client
  set recovers from; the job's verdict is `download.job.failed`.
- The sink groups a bare `%s` pass-through by its text (numbers folded), and
  a process's last batch closes the repeat window, so a short-lived download
  child still reports what it dropped.
- Worker-side failures (stall, wall-clock, no asset, cached asset error) log
  `download.job.failed` with a cause; they left no line at all before. The
  crash, supervisor-error and non-zero-exit lines carry the code too.
- An edit failure is one coded line in `_fail_edit`, for every path.
- `logs.get_logger("__main__")` resolves to the `-m` module, so the worker
  and the download child keep their names.
- TRACE lines carrying user content are gated on `logs.consented_trace()`,
  not on the process level; a contract test pins it.
- The OAuth token refresh goes through `_upstream_failure`; transport errors
  carry reason `transport`. Subscribe recognises a duplicate by reason code
  only (the prose fallback was dead).
- Once-only guards for a stale sysconfig override and a refusing HLS session
  directory; item_detail splits Plex failures from our own parse bugs.
- The playlist breaker line names the playlist and the action; comments that
  were false (runner noqa, `_merge_vtt`, sink grouping) are corrected.

backend/app/routes/plex/detail.py

@@ -405,13 +405,31 @@ def item_detail(
                         "text": codec not in subtitles.BITMAP_SUBS,
                     }
                 )
-    except Exception:  # noqa: BLE001 — playback works without the extras; never 500 here
-        # Best-effort, but not free: what this drops is the subtitle stream list and the intro
-        # markers, so the player offers no subtitles and no skip button — and looks like a file
-        # that has neither.
+    # Best-effort, but not free: what either branch drops is the subtitle stream list and the intro
+    # markers, so the player offers no subtitles and no skip button — and looks like a file that has
+    # neither.
+    except PlexNotConfigured:
+        # silent-ok: not a failure but a state — no Plex server, and nothing to play from anyway.
+        pass
+    except PlexError as exc:
         log.warning(
             "the live extras for an item could not be fetched",
-            extra=logs.event("plex.detail.extras_failed", rating_key=it.rating_key, kind=it.kind),
+            extra=logs.event(
+                "plex.detail.extras_failed",
+                rating_key=it.rating_key,
+                kind=it.kind,
+                reason=type(exc).__name__,
+            ),
+        )
+    except Exception:  # noqa: BLE001 — playback works without the extras; never 500 here
+        # Plex answered and WE could not read it — a shape our parsing does not expect. The same
+        # split `show_detail` makes: the stack is the only thing that says where.
+        log.warning(
+            "the live extras for an item could not be read",
+            extra=logs.event(
+                "plex.detail.extras_unreadable", rating_key=it.rating_key, kind=it.kind
+            ),
+            exc_info=True,
         )
 
     # Lazy enrichment (movies only): the live fetch above carries the FULL cast + rich detail (the sync