feat: pool remove_slot with file cleanup

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

gates/pool.py

@@ -61,6 +61,25 @@ def add_image(base_dir, pool_id, data, ts=0):
     return m
 
 
+def remove_slot(base_dir, pool_id, index):
+    m = read_manifest(base_dir, pool_id)
+    if index < 0 or index >= len(m["slots"]):
+        return m
+    slot = m["slots"].pop(index)
+    d = pool_dir(base_dir, pool_id)
+    for key in ("image", "mask"):
+        name = slot.get(key)
+        if name:
+            f = d / name
+            if f.exists():
+                f.unlink()
+    if index < m["active"]:
+        m["active"] -= 1
+    m["active"] = _clamp_active(m)
+    write_manifest(base_dir, pool_id, m)
+    return m
+
+
 def _clamp_active(m):
     n = len(m["slots"])
     if n == 0:

tests/test_pool.py

@@ -51,6 +51,26 @@ def test_add_image_monotonic_after_growth(tmp_path):
     assert [s["image"] for s in m["slots"]] == ["img_0001.png", "img_0002.png"]
 
 
+def test_remove_slot_deletes_files_and_reindexes(tmp_path):
+    pool.add_image(str(tmp_path), "p1", b"a", ts=1)
+    pool.add_image(str(tmp_path), "p1", b"b", ts=2)
+    pool.add_image(str(tmp_path), "p1", b"c", ts=3)
+    m = pool.set_active(str(tmp_path), "p1", 2)          # active=2
+    m = pool.remove_slot(str(tmp_path), "p1", 0)         # drop first
+    assert [s["image"] for s in m["slots"]] == ["img_0002.png", "img_0003.png"]
+    assert not (tmp_path / "p1" / "img_0001.png").exists()
+    assert m["active"] == 1                              # shifted down
+
+
+def test_remove_active_clamps(tmp_path):
+    pool.add_image(str(tmp_path), "p1", b"a", ts=1)
+    pool.add_image(str(tmp_path), "p1", b"b", ts=2)
+    pool.set_active(str(tmp_path), "p1", 1)
+    m = pool.remove_slot(str(tmp_path), "p1", 1)         # removed the active last one
+    assert m["active"] == 0
+    assert len(m["slots"]) == 1
+
+
 def test_set_active_clamps(tmp_path):
     pool.add_image(str(tmp_path), "p1", b"a", ts=1)
     pool.add_image(str(tmp_path), "p1", b"b", ts=2)