connectDuckdb() installs the ICU extension but never loads it

DatabaseConnector::connectDuckdb() runs INSTALL icu but never LOAD icu. Since LOAD is per-connection and INSTALL persists, the ICU extension ends up installed but unloaded on every connection, and functions that depend on it remain unavailable.

--- connection from DatabaseConnector: installed, not loaded ---

> library(DatabaseConnector)
> cd <- createConnectionDetails(dbms = "duckdb", server = tempfile(fileext = ".duckdb"))
> con <- connect(cd)
Connecting using DuckDB driver
> querySql(con, "SELECT value FROM duckdb_settings() WHERE name = 'autoload_known_extensions'")
  value
1  true
> querySql(con, "SELECT extension_name, installed, loaded
+                FROM duckdb_extensions() WHERE extension_name = 'icu'")
  extension_name installed loaded
1            icu      TRUE  FALSE
> querySql(con, "SELECT CAST((CURRENT_DATE + TO_DAYS(CAST(1 AS INTEGER))) AS DATE) AS x")
Error executing SQL:
Binder Error: No function matches the given name and argument types '(DATE, INTERVAL)'.
LINE 1: SELECT CAST((CURRENT_DATE + TO_DAYS(CAST(1 AS INTEGER))) AS DATE) AS x

--- same connection after LOAD ---

> executeSql(con, "LOAD icu")
> querySql(con, "SELECT CAST((CURRENT_DATE + TO_DAYS(CAST(1 AS INTEGER))) AS DATE) AS x")
           x
1 2026-09-05

--- LOAD does not carry to a new connection, INSTALL does ---

> c2 <- dbConnect(duckdb::duckdb(), dbdir = f)   # same file, fresh connection
> dbGetQuery(c2, "SELECT installed, loaded FROM duckdb_extensions()
+                 WHERE extension_name = 'icu'")
  installed loaded
1      TRUE  FALSE

Relevant lines:

https://github.com/OHDSI/DatabaseConnector/blob/128c84fa4f2fa254667dd17dc30210f7c1420a63/R/Connect.R#L863-L880

The guard queries installed rather than loaded. INSTALL writes to the DuckDB home directory and persists across sessions, so after the first successful install the branch is skipped on every subsequent connection and LOAD is never reached. LOAD icu does not appear anywhere else in the package.

Note that autoload_known_extensions is true on the connection, so DuckDB's extension autoloading does not cover this case.

Encountered via DataQualityDashboard::executeDqChecks() against a DuckDB CDM, where plausibleValueHigh on CDM_SOURCE.CDM_RELEASE_DATE renders as CURRENT_DATE + TO_DAYS(...) and reports an error rather than a result.

Environment:

DatabaseConnector: 7.2.0
duckdb: 1.5.5
DataQualityDashboard: 2.8.9
R: 4.6.0, macOS

Start in R/Connect.R at lines 863-880 and inspect how connectDuckdb() checks and handles the ICU extension. Reproduce the connection with the DuckDB queries in the issue, then verify that a fresh connection reports ICU as loaded and the date expression succeeds.