perf: eliminate theme switch lag by suppressing CSS transitions

Disable all CSS transitions/animations during theme toggle so color
changes apply instantly instead of animating over 150ms. Also cache
Tauri window module import and set color-scheme for native UI elements.

src-tauri/src/commands/agents.rs

@@ -17,6 +17,7 @@ const AGENT_TYPES: &[(&str, &str)] = &[
     ("vastbase", "Vastbase"),
     ("goldendb", "GoldenDB"),
     ("oracle", "Oracle"),
+    ("oracle-10g", "Oracle 10g"),
     ("h2", "H2"),
     ("snowflake", "Snowflake"),
     ("trino", "Trino (Presto)"),