fix(ingest): skip tier-gated Patreon posts entirely (#874)

Patreon serves only blurred locked-preview thumbnails for posts the
authenticated account can't fully view; the native ingester was
downloading those as real media. current_user_can_view was already in
_FIELDS_POST but never read.

Add PatreonClient.post_is_gated (gate ONLY on explicit
current_user_can_view=False; missing/None → viewable, never over-filter)
and skip gated posts at the top of the ingest_core run() and preview()
loops — no media download AND no post-record stub (operator: 'no stub
for gated content'). Skipped before the post-record block so gated posts
never inflate the #862 body canary; surfaced as 'N gated-skipped' in the
run summary. Same gate in preview() for preview/apply parity (rule 93).

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

tests/test_patreon_client.py

@@ -435,3 +435,27 @@ def test_post_record_key_returns_synthetic_key_and_id():
 def test_post_record_key_none_without_id():
     assert PatreonClient.post_record_key({}) is None
     assert PatreonClient.post_record_key({"id": None}) is None
+
+
+# -- post_is_gated (#874 tier-gated access filter) --------------------------
+
+
+def test_post_is_gated_only_on_explicit_false():
+    # The blurred-preview case: account can't view the post → gate it.
+    assert PatreonClient.post_is_gated(
+        {"attributes": {"current_user_can_view": False}}
+    ) is True
+
+
+def test_post_is_gated_viewable_and_missing_are_not_gated():
+    # Explicit True, a missing flag, an explicit None, and a missing attributes
+    # block ALL count as viewable — gate only on an explicit False so an absent
+    # field never over-filters accessible posts.
+    assert PatreonClient.post_is_gated(
+        {"attributes": {"current_user_can_view": True}}
+    ) is False
+    assert PatreonClient.post_is_gated({"attributes": {}}) is False
+    assert PatreonClient.post_is_gated(
+        {"attributes": {"current_user_can_view": None}}
+    ) is False
+    assert PatreonClient.post_is_gated({}) is False