ci: Add ORA_TZFILE workaround to ruby_head workflow

The scheduled ruby_head workflow has been failing since 2026-05-09 with
`OCIError: ORA-01805: possible error in date/time operation` raised from
`ocidatetime.c:119` for every DATE/TIMESTAMP fetch:

    https://github.com/rsim/ruby-plsql/actions/runs/25586756343

Cause: `gvenzl/oracle-free:latest` ships Oracle Free 23ai with a newer
timezone-data version than the `instantclient-basic-linuxx64.zip` "latest"
download embeds, and ruby-oci8 raises ORA-01805 whenever the client tries
to materialize a date/time fetched from a session opened against the newer
server.

Copy the server's `timezlrg_*.dat` onto the Instant Client and point
ORA_TZFILE at it, immediately after the `Create database user` step.
The lookup is dynamic so a future bump of the gvenzl image (which ships
whatever timezone version is current) continues to work without further
edits.

Mirrors rsim/oracle-enhanced#2764.

Author: yahonda

.github/workflows/ruby_head.yml

@@ -62,6 +62,17 @@ jobs:
     - name: Create database user
       run: |
         ./ci/setup_accounts.sh
+    - name: Force client TZ data to match server (ORA_TZFILE workaround)
+      run: |
+        ORACLE_CONTAINER=$(docker ps --filter "ancestor=gvenzl/oracle-free" -q)
+        SRC=$(docker exec "$ORACLE_CONTAINER" bash -c 'ls $ORACLE_HOME/oracore/zoneinfo/timezlrg_*.dat 2>/dev/null | head -1')
+        echo "Server TZ file: $SRC"
+        DST_DIR="$ORACLE_HOME/oracore/zoneinfo"
+        sudo mkdir -p "$DST_DIR"
+        docker cp "$ORACLE_CONTAINER":"$SRC" /tmp/_server_tzfile.dat
+        sudo mv /tmp/_server_tzfile.dat "$DST_DIR/$(basename "$SRC")"
+        ls -l "$DST_DIR"
+        echo "ORA_TZFILE=$DST_DIR/$(basename "$SRC")" >> $GITHUB_ENV
     - name: Bundle install
       run: |
         bundle install --jobs 4 --retry 3