docs(recovery): document spacemap/import recovery (Fixes #16461)

Author: 2400032703kotinijeswanth

docs/Recovering-Pool-Import-Issue.md

@@ -0,0 +1,11 @@
+# Recovering an “ONLINE but Cannot Import” Pool
+
+If `zpool import` lists a pool as ONLINE but it fails to import, the metadata or spacemap may be corrupted.
+
+## Recovery Procedure
+
+```bash
+zpool import -Fn <pool>
+zpool import -F <pool>
+zpool import -FX <pool>
+zpool import -o readonly=on <pool>