Stop trusting Plex's Date Added on its own

Jess spotted that dates looked like file dates rather than library-add dates.
He is right, and MediaShelf was not the culprit: it reproduces Plex's addedAt
exactly (verified 500/500 identical to the second). Plex's own field is what
follows the file — replace or re-encode one and Date Added resets while the
item, its ratingKey and its watch history all survive.

Measured on the live library, comparing addedAt against lastViewedAt where both
exist: 55 of 509 movies (10.8%) and 306 of 1,393 TV Show Archive items (22.0%)
were watched BEFORE they were "added" — 19% overall. 2001: A Space Odyssey
reports added 2026-07-31, last watched 2017-08-26.

That is not cosmetic. pre_history is derived from added_at, so an old item whose
file was replaced looks post-coverage and gets promoted into the CONFIDENT
reclaim pool, which is the one pool meant to be trustworthy.

A completed play proves the item already existed, so added_at is now
MIN(provider_added_at, first_watched_at). Plex's raw value is kept in
provider_added_at, added_at_source records which applied, and the item drawer
explains the substitution instead of quietly disagreeing with Plex. Unwatched
items keep Plex's value since nothing contradicts it. first_seen_at is also
recorded now and is authoritative for anything added from here on.

Plex's API has no better field; the true insert time is only in Plex's own
metadata_items.created_at on Loki.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GVbG48GAXfCZatcmX123Ra

tests/test_ingest.py

@@ -138,3 +138,53 @@ def test_episodes_without_a_parent_rating_key_still_build_a_season(scanned):
 def test_no_orphan_episode_warnings(scanned, rescan):
     r = rescan("full")
     assert not [w for w in (r.warnings or []) if "no season" in w]
+
+
+def test_added_at_is_corrected_when_plex_claims_it_postdates_a_play(scanned):
+    """Plex's addedAt follows the file, so replacing one resets Date Added while
+    the watch history survives. A play proves the item already existed."""
+    row = scanned.one("SELECT * FROM media_item WHERE title = 'Replaced File'")
+    assert row is not None
+
+    assert row["provider_added_at"] > row["first_watched_at"], \
+        "fixture should present an addedAt later than the first play"
+    assert row["added_at"] == row["first_watched_at"], \
+        "added_at was not pulled back to the first play"
+    assert row["added_at_source"] == "first_watch"
+
+
+def test_correction_leaves_unwatched_items_alone(scanned):
+    """Nothing contradicts Plex for an item nobody ever played."""
+    rows = scanned.query(
+        "SELECT * FROM media_item WHERE kind='movie' AND watch_count = 0 "
+        "AND provider_added_at IS NOT NULL LIMIT 20")
+    assert rows
+    for r in rows:
+        assert r["added_at"] == r["provider_added_at"]
+        assert r["added_at_source"] == "provider"
+
+
+def test_corrected_date_moves_the_item_into_the_uncertain_pool(scanned):
+    """The reason this matters: pre_history is derived from added_at, so a
+    wrongly-recent date promotes an item into the CONFIDENT reclaim pool."""
+    row = scanned.one("SELECT * FROM media_item WHERE title = 'Replaced File'")
+    cov = scanned.one("SELECT earliest_event_at FROM history_coverage LIMIT 1")
+    if row["added_at"] < cov["earliest_event_at"]:
+        assert row["pre_history"] == 1
+
+
+def test_first_seen_at_is_recorded(scanned):
+    n = scanned.scalar("SELECT COUNT(*) FROM media_item WHERE first_seen_at IS NULL "
+                       "AND kind='movie'")
+    assert n == 0, "first_seen_at should be stamped on every row MediaShelf creates"
+
+
+def test_added_at_correction_is_idempotent(scanned, rescan):
+    before = scanned.query(
+        "SELECT id, added_at, provider_added_at, added_at_source FROM media_item "
+        "ORDER BY id")
+    rescan("full")
+    after = scanned.query(
+        "SELECT id, added_at, provider_added_at, added_at_source FROM media_item "
+        "ORDER BY id")
+    assert [dict(r) for r in before] == [dict(r) for r in after]