feat: a tick keeps looking back 30 days, so an EDITED post is reached (4386)

Operator, 2026-09-23, on a Floppystack post: "this post has been updated as
he implements hot fixes — any chance we have a way to scan for or see updated
posts so we can update ours to match and pull the new attachments and
pictures etc."

The download half already worked: extract_media reads the media list off the
LIVE feed response every walk, so a newly attached hotfix build is a ledger
key we have never seen. Only REACHING the post was missing — a tick stopped
after 20 contiguous already-have-it items, and a post edited three days after
publication sits well below twenty. Not a bug in the early-out; a count
cannot express "recent".

The early-out now needs BOTH conditions: the run of seen items AND a post
published before the horizon. Strictly a widening — window 0 is exactly the
old behaviour, and no window can make a tick stop EARLIER than it used to, so
a source paused for months still walks its whole unseen backlog. The horizon
is a floor on how far to look, never a ceiling.

Inside the window the post-record gate is bypassed too (write_post_record
revisit=True): the body is re-read from the feed response already in hand, so
a revisit costs zero requests, and a body that comes back empty writes
NOTHING rather than blanking one a detail-fetch had filled. Revisits are kept
out of the #862 body-drift canary's sample for the same reason — an empty
revisit is healthy, and counting it would walk the alarm toward firing on
good ticks.

The run summary names what changed ("3 post(s) updated (5 new file(s))") with
a line per post; the ask was to SEE updated posts, not only to end up with
their bytes.

download_revisit_days is a settings row, not a constant (rule 25) — how long
a creator keeps editing is a property of the creator. Default 30, 0 turns it
off. Migration 0108.

Also corrects two stale docstrings: both clients described post_meta as
feeding an Ingester.preview that no longer calls it. It had no consumer at
all until this change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

tests/test_patreon_downloader.py

@@ -658,6 +658,53 @@ def test_write_post_record_writes_enriched_post_only_sidecar(tmp_path):
     assert rec.body_chars == len("<p>text post body</p>")
 
 
+# The revisit contract (2026-09-23): a tick re-reading a post it already
+# captured, so an edit made after first capture reaches us. Both halves exist to
+# stop an update costing more than it is worth.
+
+
+def test_a_revisit_re_reads_the_body_without_paying_for_a_detail_fetch(tmp_path):
+    """A 30-day window would otherwise buy one detail GET per body-less post per
+    tick, forever — a per-creator cost that grows with how prolific they are, to
+    re-fetch a body we already stored."""
+    calls: list[str] = []
+
+    def _fetcher(post_id: str) -> str:
+        calls.append(post_id)
+        return "<p>detail body</p>"
+
+    dl = PatreonDownloader(
+        images_root=tmp_path, cookies_path=None, validate=False,
+        session=_FakeSession(), content_fetcher=_fetcher,
+    )
+    post = _post()
+    post["attributes"]["content"] = "<p>feed body</p>"
+    rec = dl.write_post_record(post, "artist-x", revisit=True)
+
+    assert calls == []
+    assert json.loads(rec.path.read_text())["content"] == "<p>feed body</p>"
+
+
+def test_a_revisit_with_an_empty_body_writes_nothing_at_all(tmp_path):
+    """The data-loss guard. On a FIRST capture an empty body is the truth about
+    the post; on a revisit it usually means the body only ever came from the
+    detail endpoint we just declined to call. Writing it would blank a stored
+    body to say something we never learned."""
+    dl = PatreonDownloader(
+        images_root=tmp_path, cookies_path=None, validate=False,
+        session=_FakeSession(), content_fetcher=lambda _pid: "<p>detail</p>",
+    )
+    post = _post()
+    post["attributes"]["content"] = ""
+    rec = dl.write_post_record(post, "artist-x", revisit=True)
+
+    assert rec.path is None
+    assert rec.body_chars == 0
+    # Not "wrote an empty file" — nothing was written, so a record captured on
+    # an earlier walk is still exactly what it was.
+    assert not list(tmp_path.rglob("_post.json"))
+
+
 def test_write_post_record_none_without_post_id(tmp_path):
     dl = PatreonDownloader(
         images_root=tmp_path, cookies_path=None, validate=False,