test(patreon): adjust deterministic clock for the new per-media should_stop read

The mid-post time-box check (619e771) reads time.monotonic() once more per post,
so test_backfill_budget_cut_returns_partial_with_progress's discrete tick
sequence shifted — the >budget tick (200) landed on post1's first-item check
instead of post2's gate, cutting post1 to 0 files. Add the extra tick (20, still
under budget) so post1's item downloads, matching production where the gate and
the first should_stop are microseconds apart.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_patreon_ingester.py

@@ -349,11 +349,14 @@ async def test_tick_does_not_checkpoint_cursor(source_id, sync_engine, tmp_path,
 async def test_backfill_budget_cut_returns_partial_with_progress(
     source_id, sync_engine, tmp_path, monkeypatch,
 ):
-    # Deterministic clock: start=0, post1 check=10 (ok), post2 check=200 (>budget).
-    # run() lives in ingest_core now, so patch the clock there (the same global
-    # time module object, but we reference it through the module that uses it).
+    # Deterministic clock: start=0; post1 gate=10 (ok); post1's per-media
+    # should_stop=20 (still ok, so post1's item downloads); post1 live-progress
+    # read=200; post2 gate=250 (>budget → cut). The per-media should_stop check
+    # (added 2026-06-07 to bound media-dense posts) reads the clock once more per
+    # post, so the sequence carries the extra tick. run() lives in ingest_core
+    # now, so patch the clock there.
     import backend.app.services.ingest_core as core
-    ticks = iter([0.0, 10.0, 200.0, 250.0])
+    ticks = iter([0.0, 10.0, 20.0, 200.0, 250.0])
     last = [0.0]
 
     def fake_monotonic():