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_subscribestar_native.py

@@ -453,6 +453,29 @@ def test_write_post_record(tmp_path):
     assert rec.body_chars > 0
 
 
+def test_a_revisit_with_an_empty_body_writes_nothing(tmp_path):
+    """The revisit contract's second half, which applies here even though the
+    first (no detail-fetch) is free on SubscribeStar — there is no detail
+    endpoint. A chunk that parsed with no content must not overwrite a body we
+    already have, so a walk behaves the same on both platforms."""
+    dl = _downloader(tmp_path)
+    post = _post("222")
+    post["attributes"]["content"] = ""
+    rec = dl.write_post_record(post, "artist-x", revisit=True)
+
+    assert rec.path is None
+    assert rec.body_chars == 0
+    assert not list(tmp_path.rglob("_post.json"))
+
+
+def test_a_revisit_that_still_has_a_body_writes_it(tmp_path):
+    dl = _downloader(tmp_path)
+    rec = dl.write_post_record(_post("333"), "artist-x", revisit=True)
+
+    assert rec.path is not None
+    assert "body text" in json.loads(rec.path.read_text())["content"]
+
+
 def test_skip_seen_does_not_download(tmp_path):
     session = _FakeSession()
     dl = _downloader(tmp_path, session=session)