feat(poc): rewind MCP, skill, and recover-ladder docs

Initial PoC: find_protection, tagged checkpoints, FLR, mutating catalog.
Lab 10.9 status enums (0=Initializing, 1=MeetingSLA). Credentials stay in gitignored config.json.

tests/test_checkpoints.py

@@ -0,0 +1,24 @@
+from datetime import UTC, datetime
+
+from zerto_rewind_mcp.checkpoints import checkpoint_id, checkpoint_tag, make_tag
+
+
+def test_tag_format():
+    when = datetime(2026, 9, 21, 15, 4, 5, tzinfo=UTC)
+    tag = make_tag("codex", "chg-99", when)
+    assert tag == "ai:codex:chg-99:20260921T150405Z"
+
+
+def test_tag_strips_junk():
+    tag = make_tag("agent one", "path/with spaces", datetime(2026, 1, 1, tzinfo=UTC))
+    assert " " not in tag
+    assert tag.startswith("ai:agent-one:path-with-spaces:")
+
+
+def test_checkpoint_row_keys():
+    row = {"CheckpointId": "cp-1", "Tag": "ai:x:y:z", "Timestamp": 1}
+    assert checkpoint_id(row) == "cp-1"
+    assert checkpoint_tag(row) == "ai:x:y:z"
+    row2 = {"checkpointId": "cp-2", "tag": "t"}
+    assert checkpoint_id(row2) == "cp-2"
+    assert checkpoint_tag(row2) == "t"