fix: close data integrity and hot-reload review findings

Backfill same-day snapshots for newly added or restored videos, preserve successful fan snapshots on resume, persist incomplete state before forced re-runs, and split collection completion from backup completion so failed backups can retry without API calls. Reject missing data payloads instead of treating them as empty folders, guard against mass-unfav on suspicious empty remote folders, rebuild Bilibili clients when credentials change, recompute primary folder ownership from active relations with per-folder fav_time, preserve original titles for dropped invalid videos, poll config every 60 seconds, and fix favsort verify interval and mixed resource types.

tests/test_provider.py

@@ -0,0 +1,106 @@
+# -*- coding: utf-8 -*-
+"""凭据变化时客户端重建测试（不联网）: uv run python tests/test_provider.py"""
+
+import json
+import os
+import sys
+import tempfile
+import time
+from pathlib import Path
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+sys.stdout.reconfigure(encoding="utf-8")
+
+from reaction_board.bilibili.client import BilibiliClient, Pacer  # noqa: E402
+from reaction_board.bilibili.provider import ClientProvider  # noqa: E402
+from reaction_board.config import ConfigStore  # noqa: E402
+
+
+def write_config(path: Path, *, cookie: str, mid: int) -> None:
+    path.write_text(json.dumps({
+        "bilibili": {
+            "read": {"mid": mid, "csrf": "read-csrf", "cookie": cookie},
+            "write": {"mid": 2, "csrf": "write-csrf", "cookie": "write-cookie"},
+        },
+        "folders": [],
+    }, ensure_ascii=False), encoding="utf-8")
+
+
+def bump(path: Path) -> None:
+    target = max(path.stat().st_mtime_ns, time.time_ns()) + 1_000_000
+    os.utime(path, ns=(target, target))
+
+
+def test_rebuild_only_when_credentials_change():
+    with tempfile.TemporaryDirectory() as tmp:
+        path = Path(tmp) / "config.json"
+        write_config(path, cookie="cookie-a", mid=1)
+        store = ConfigStore(path, env={})
+        created = []
+
+        def factory(credentials):
+            created.append((credentials.mid, credentials.cookie))
+            return BilibiliClient(
+                cookie=credentials.cookie,
+                csrf=credentials.csrf,
+                mid=credentials.mid,
+                pacer=Pacer(1.0, 1.6),
+            )
+
+        provider = ClientProvider(store, "read", factory)
+        first = provider.get()
+        assert provider.get() is first
+        assert created == [(1, "cookie-a")]
+
+        write_config(path, cookie="cookie-b", mid=1)
+        bump(path)
+        second = provider.get()
+        assert second is not first
+        assert created == [(1, "cookie-a"), (1, "cookie-b")]
+        assert second.pacer.min_delay == 1.0
+        assert second.pacer.max_delay == 1.6
+
+        # 仅 mtime 变化但凭据相同：不重建
+        bump(path)
+        assert provider.get() is second
+        assert len(created) == 2
+
+
+def test_mid_change_rebuilds():
+    with tempfile.TemporaryDirectory() as tmp:
+        path = Path(tmp) / "config.json"
+        write_config(path, cookie="cookie-a", mid=1)
+        store = ConfigStore(path, env={})
+        provider = ClientProvider(
+            store, "read",
+            lambda credentials: BilibiliClient(mid=credentials.mid),
+        )
+        assert provider.get().mid == 1
+        write_config(path, cookie="cookie-a", mid=9)
+        bump(path)
+        assert provider.get().mid == 9
+
+
+def test_config_revision_increments():
+    with tempfile.TemporaryDirectory() as tmp:
+        path = Path(tmp) / "config.json"
+        write_config(path, cookie="cookie-a", mid=1)
+        store = ConfigStore(path, env={})
+        assert store.revision == 0
+        write_config(path, cookie="cookie-b", mid=1)
+        bump(path)
+        store.get()
+        assert store.revision == 1
+        store.get()
+        assert store.revision == 1
+
+
+def main():
+    test_rebuild_only_when_credentials_change()
+    test_mid_change_rebuilds()
+    test_config_revision_increments()
+    print("OK: 凭据变化重建客户端与配置 revision 测试全部通过")
+
+
+if __name__ == "__main__":
+    main()