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/patreon_downloader.py

@@ -151,6 +151,20 @@ class MediaOutcome:
     error: str | None
 
 
+@dataclass
+class PostRecordOutcome:
+    """Result of write_post_record — mirrors the download_post → MediaOutcome
+    contract so the engine reports per-post handling without re-reading the post.
+    `path` is the _post.json sidecar (None when the post had no id); the rest is
+    the captured body's shape (post_type + final char count) for the run log.
+    """
+
+    path: Path | None
+    post_type: str | None
+    title: str | None
+    body_chars: int
+
+
 class PatreonDownloader:
     """Download resolved Patreon media to gallery-dl's on-disk layout.
 
@@ -567,27 +581,33 @@ class PatreonDownloader:
         sidecar_path.write_text(json.dumps(data, indent=2))
         return sidecar_path
 
-    def write_post_record(self, post: dict, artist_slug: str) -> Path | None:
+    def write_post_record(self, post: dict, artist_slug: str) -> PostRecordOutcome:
         """Write a post-ONLY sidecar (no media file) for a media-less post, so
         the importer can still upsert the Post + its body — text posts often hold
         the only copy of an external <a href> link. Named `_post.json`: the
         leading underscore keeps it from colliding with a media sidecar
         (`<NN>_<stem>.json`) and from being resolved as some media file's sidecar
-        by find_sidecar. Returns the path, or None when the post has no id."""
+        by find_sidecar.
+
+        Returns a PostRecordOutcome (path None when the post has no id) carrying
+        the captured body's shape — post_type + final char count — so the engine
+        can log per-post handling without re-reading the post itself.
+        """
+        attrs = post.get("attributes") or {}
+        title = attrs.get("title") if isinstance(attrs.get("title"), str) else None
+        post_type = attrs.get("post_type") if isinstance(attrs.get("post_type"), str) else None
         pid = str(post.get("id") or "")
         if not pid:
-            return None
+            return PostRecordOutcome(
+                path=None, post_type=post_type, title=title, body_chars=0,
+            )
         post_dir = self.images_root / artist_slug / "patreon" / _post_dir_name(post)
         post_dir.mkdir(parents=True, exist_ok=True)
         path = self._write_sidecar_data(post, post_dir / "_post.json")
-        # Per-post body-capture diagnostic: _write_sidecar_data has, by now,
-        # memoized any detail-fetched body onto post["attributes"]["content"], so
-        # this reflects the FINAL body (feed or detail). Logs the success (N chars)
-        # AND the skip (empty) so a recapture's per-post outcome is visible.
+        # _write_sidecar_data has by now memoized any detail-fetched body onto
+        # post["attributes"]["content"], so re-read it for the FINAL char count.
         body = (post.get("attributes") or {}).get("content")
-        n = len(body) if isinstance(body, str) else 0
-        if n:
-            log.info("post-record: post %s body captured (%d chars)", pid, n)
-        else:
-            log.info("post-record: post %s has NO body (feed + detail both empty)", pid)
-        return path
+        body_chars = len(body) if isinstance(body, str) else 0
+        return PostRecordOutcome(
+            path=path, post_type=post_type, title=title, body_chars=body_chars,
+        )