Implement tab-scoped runs pagination state

tests/test_tab_state.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from datetime import UTC, datetime, timedelta
+
+from repub.datastar import TabStateStore
+
+
+def test_tab_state_store_tracks_page_state_per_tab_and_connection_count() -> None:
+    store = TabStateStore()
+
+    store.connect("tab-1")
+    store.connect("tab-1")
+    store.update_page_state(
+        "tab-1",
+        "runs",
+        lambda state: {**state, "completed_page": 2},
+    )
+
+    assert store.get_tab_state("tab-1") == {"runs": {"completed_page": 2}}
+
+    store.disconnect("tab-1")
+
+    assert store.get_tab_state("tab-1") == {"runs": {"completed_page": 2}}
+
+    store.disconnect("tab-1")
+
+    assert store.get_tab_state("tab-1") is None
+
+
+def test_tab_state_store_cleans_only_stale_disconnected_tabs() -> None:
+    store = TabStateStore(clean_age_threshold=timedelta(hours=24))
+    now = datetime(2026, 3, 31, 12, 0, tzinfo=UTC)
+
+    store.connect("stale-tab", now=now - timedelta(days=2))
+    store.connect("fresh-tab", now=now)
+
+    removed = store.cleanup_stale(now=now)
+
+    assert removed == {"stale-tab"}
+    assert store.get_tab_state("stale-tab") is None
+    assert store.get_tab_state("fresh-tab") == {}