wallet/docs: SQLite is the default backend, not experimental

Drop the "experimental" label from the wallet code and docs now that
SQLite is the default backend for new wallets, is coin-proven, and carries
encrypt, backup, atomic seed writes, and the storage diagnostics.

- main_gui.cpp: -help text, the unknown-backend error (SQLite is no longer
  "experimental" and Berkeley DB is no longer "the default"), and the
  startup banner ("Wallet backend: SQLite").
- walletcmd.h: the export command comment.
- docs/storage.md: rewrite the SQLite section from staging-only ("runtime
  still opens Berkeley DB", "no runtime backend flag exists yet") to the
  shipped state -- default backend, conversion wizard, per-backend ops --
  and reframe the migration order as shipped in v1.2.20.

2 files changed, 11 insertions, 11 deletions

diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index 55ca8c6..943799f 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -182,7 +182,7 @@ static void PrintUsage()
     printf("  /walletstoragecheck        (fail closed on inconsistent or unsafe\n");
     printf("                              wallet.dat storage state)\n");
     printf("  /walletsqliteexport=FILE   (copy raw wallet.dat records into an\n");
-    printf("                              experimental SQLite store, then exit)\n");
+    printf("                              SQLite store, then exit)\n");
     printf("  /walletsqliteverify=FILE   (compare wallet.dat with a SQLite export,\n");
     printf("                              printing counts only, then exit)\n");
     printf("  /walletsqliterestore=FILE  (rebuild wallet.dat from a SQLite export in\n");
@@ -680,17 +680,17 @@ int main(int argc, char* argv[])
             AttachTerminal();
             FatalStartupError(fHeadlessStartup,
                 strprintf("Unknown wallet backend '%s'.", strWalletBackend.c_str()),
-                "Use -walletbackend=sqlite for the experimental SQLite backend, "
-                "or omit -walletbackend (or -walletbackend=bdb) to use the "
-                "default Berkeley DB wallet.dat.");
+                "Use -walletbackend=sqlite for the SQLite backend, or "
+                "-walletbackend=bdb for the Berkeley DB wallet.dat.");
             return 1;
         }
 
         if (strWalletBackend == "sqlite")
         {
-            // Opt-in, experimental. The node runs on <datadir>/wallet.sqlite and
-            // never opens wallet.dat, but the user has to have exported one
-            // first -- there is no silent migration, and wallet.dat is left
+            // Explicit opt-in via the flag. The node runs on
+            // <datadir>/wallet.sqlite and never opens wallet.dat, but the user
+            // has to have exported one first -- there is no silent migration,
+            // and wallet.dat is left
             // exactly where it is so a plain restart goes back to it.
             AttachTerminal();
             string strSQLitePath = GetAppDir() + "/wallet.sqlite";
@@ -724,7 +724,7 @@ int main(int argc, char* argv[])
             }
 
             fprintf(stderr,
-                    "Wallet backend: SQLite (experimental)\n"
+                    "Wallet backend: SQLite\n"
                     "  %s\n"
                     "Your Berkeley DB wallet.dat is left untouched. Restart without\n"
                     "-walletbackend=sqlite to go back to it.\n",
diff --git a/src/walletcmd.h b/src/walletcmd.h
index 38cbfdb..7013d44 100644
--- a/src/walletcmd.h
+++ b/src/walletcmd.h
@@ -70,9 +70,9 @@ int CmdWalletStorageAudit(const std::string& strJsonOut = "");
 // or migration-unsafe mix of storage records.
 int CmdWalletStorageCheck();
 
-// Diagnostic/migration staging: copy every raw wallet.dat record into an
-// experimental SQLite key/value store, preserving serialized bytes. This does
-// not change which backend the runtime wallet opens.
+// Copy every raw wallet.dat record into a SQLite key/value store, preserving
+// serialized bytes. A migration/scripting tool; it does not change which backend
+// the runtime wallet opens.
 int CmdWalletSQLiteExport(const std::string& strDest);
 
 // Export the currently-loaded wallet to a SQLite file (shared by the command