fix(patreon): full-fetch fallback when sparse fieldset returns null content (#842)

Operator-flagged: 9 StickySpoodge posts had empty bodies in FC despite the body
plainly existing + being accessible (creds refresh didn't help). All 9 are
body-only / poll / embed / announcement posts with no downloadable gallery
media — Patreon's detail endpoint returns content:null for these under the
sparse fields[post]=content request even though the body exists.

fetch_post_detail_content now re-fetches the FULL post resource once when the
sparse request comes back empty: recovers the body when the sparse fieldset was
the cause, and logs post_type when even the full resource is empty (body lives
elsewhere). Only the empty cases pay the extra GET; the 126 already-working
posts keep the fast sparse path.

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

tests/test_patreon_client.py

@@ -380,6 +380,28 @@ def test_fetch_post_detail_content_empty_body_is_none(monkeypatch):
     assert client.fetch_post_detail_content("42") is None
 
 
+def test_fetch_post_detail_content_falls_back_to_full_fetch(monkeypatch):
+    """#842: when the sparse fields[post]=content request returns null (Patreon
+    does this for polls / embeds / body-only posts), a one-time FULL re-fetch
+    recovers the body — so inline-only / no-media posts still get their text."""
+    client = PatreonClient(cookies_path=None)
+    seen_params: list = []
+
+    def _get(url, params=None, timeout=None):
+        seen_params.append(params or {})
+        if "fields[post]" in (params or {}):
+            return _FakeResp(200, json_data={"data": {"attributes": {"content": None}}})
+        return _FakeResp(200, json_data={
+            "data": {"attributes": {"content": "<p>body via full</p>", "post_type": "poll"}}
+        })
+
+    monkeypatch.setattr(client._session, "get", _get)
+    assert client.fetch_post_detail_content("42") == "<p>body via full</p>"
+    # Sparse request first, then a full re-fetch without the sparse fieldset.
+    assert "fields[post]" in seen_params[0]
+    assert "fields[post]" not in seen_params[1]
+
+
 def test_fetch_post_detail_content_blank_id_skips_request(monkeypatch):
     calls: list = []
     client = PatreonClient(cookies_path=None)