refactor(ingest): per-post handling into run stdout via a downloader outcome (#842)

Two corrections from operator review:
1. Reuse the existing 'Raw stdout' panel instead of a bespoke structured UI
   section — the native ingester now writes a per-post line into the run stdout
   (parity with gallery-dl's per-file stdout), so the per-post handling shows in
   the panel the operator already uses.
2. DRY: stop re-reading post['attributes'] inline in ingest_core. write_post_record
   now returns a PostRecordOutcome (path, post_type, title, body_chars) — mirroring
   the download_post -> MediaOutcome contract — and the downloader owns the read;
   ingest_core only formats the outcome into the log line.

Reverts the post_diagnostics metadata field + DownloadDetailModal 'Post capture'
section added earlier. Per-post line: 'post <id> [<post_type>] body: N chars' (+
' — EMPTY' when 0), so an empty body is self-explanatory by post_type.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/app/services/ingest_core.py

@@ -143,11 +143,6 @@ class Ingester:
         # media, so phase 3 can backfill the ImageRecord's source_filehash WITHOUT
         # re-downloading or unlinking the file. Empty outside recapture mode.
         relink: list[tuple[str, str]] = []
-        # #842: per-post body-capture diagnostics surfaced on the DownloadEvent so
-        # the operator can see IN THE UI how each post was handled — crucially the
-        # post_type + final body length, which explains an empty body (e.g. a poll
-        # whose body the API never returns) without digging through worker logs.
-        post_diag: list[dict] = []
         downloaded = 0
         errors = 0
         quarantined = 0
@@ -185,7 +180,6 @@ class Ingester:
                 written_paths=written,
                 post_record_paths=list(post_records),
                 relink_source_paths=list(relink),
-                post_diagnostics=list(post_diag),
                 stdout="\n".join(log_lines),
                 stderr="",
                 return_code=return_code,
@@ -266,23 +260,20 @@ class Ingester:
                             else self._seen_keys(source_id, [pkey])
                         )
                         if pkey not in already:
-                            rec_path = write_post_record(post, artist_slug)
-                            if rec_path is not None:
-                                post_records.append(str(rec_path))
+                            rec = write_post_record(post, artist_slug)
+                            if rec.path is not None:
+                                post_records.append(str(rec.path))
                                 self._mark_seen(source_id, [(pkey, ppid)])
-                            # Read the FINAL body (write_post_record memoized any
-                            # detail-fetched content onto the post) + post_type
-                            # (already in the feed fieldset) for the per-post UI
-                            # diagnostic. A body_chars of 0 with the post_type is
-                            # the operator's "why is this one empty" answer.
-                            pattrs = post.get("attributes") or {}
-                            pbody = pattrs.get("content")
-                            post_diag.append({
-                                "post_id": ppid,
-                                "title": pattrs.get("title") or None,
-                                "post_type": pattrs.get("post_type") or None,
-                                "body_chars": len(pbody) if isinstance(pbody, str) else 0,
-                            })
+                            # Per-post handling line in the run stdout (the existing
+                            # "Raw stdout" panel) — the downloader already read the
+                            # post; we only format its outcome here. post_type beside
+                            # a 0-char body is the "why is this one empty" answer.
+                            log_lines.append(
+                                f"  post {ppid} [{rec.post_type or '?'}] "
+                                f"body: {rec.body_chars} chars"
+                                + ("" if rec.body_chars else " — EMPTY")
+                                + (f" — {rec.title}" if rec.title else "")
+                            )
 
                 media = self.client.extract_media(post, included)
                 if not media: