fix(plex): E30 review round 3 — a dead headshot breaks the Plex-failing streak, 410 held by a test

backend/app/plex/people.py

@@ -244,7 +244,8 @@ def warm_portraits(db: Session, limit: int) -> dict:
         ).tuples()
         if thumb
     }
-    done = dead = plex_failed = down = 0  # `down` counts in a row, `plex_failed` in all
+    # `down` counts Plex failing in a row (any answer from Plex breaks it), `plex_failed` in all
+    done = dead = plex_failed = down = 0
     with plex:
         for pid in people_by_credits(db, "portrait", None):
             if done + dead >= limit or down >= _PLEX_DOWN_AFTER:
@@ -264,7 +265,7 @@ def warm_portraits(db: Session, limit: int) -> dict:
                 # Plex failing, which must neither mark the file nor keep the run going.
                 cause = exc.__cause__
                 if isinstance(cause, httpx.HTTPStatusError) and cause.response.status_code in _DEAD:
-                    dead += 1
+                    dead, down = dead + 1, 0  # Plex answered: it is up, the streak is broken
                     imgcache.mark_miss(key)
                 else:
                     plex_failed, down = plex_failed + 1, down + 1