feat(agent): pluggable database drivers via JDBC agent subprocess

Migrate domestic database support (DaMeng, KingBase, Vastbase, GoldenDB) from
built-in ODBC/protocol drivers to standalone Java agent processes communicating
via stdin/stdout JSON-RPC 2.0. Agents are distributed as fat JARs with embedded
JDBC drivers, downloaded on-demand from GitHub Releases with proxy fallback.

- Add AgentDriverClient for subprocess lifecycle + JSON-RPC communication
- Add AgentManager for JRE/JAR install state management
- Add Tauri commands for driver install/uninstall/list
- Add DriverManager UI panel in settings dialog
- Extend DatabaseType with Kingbase, Vastbase, Goldendb variants
- Migrate Dameng from ODBC (dm_driver.rs) to JDBC agent
- Delete dm_driver.rs (343 lines)
- Add GitHub proxy fallback for downloads (update.hwdns.net, gh-proxy.org)

Agent code lives at https://github.com/t8y2/dbx-agents

src/stores/connectionStore.ts

@@ -159,6 +159,9 @@ export const useConnectionStore = defineStore("connection", () => {
       redshift: "Redshift",
       dameng: "DM (Dameng)",
       gaussdb: "GaussDB",
+      kingbase: "KingBase",
+      vastbase: "Vastbase",
+      goldendb: "GoldenDB",
     };
 
     const profile = config.driver_profile || config.db_type;
@@ -167,6 +170,12 @@ export const useConnectionStore = defineStore("connection", () => {
       dbType = "gaussdb" as ConnectionConfig["db_type"];
     } else if (profile === "redshift" && dbType === "postgres") {
       dbType = "redshift" as ConnectionConfig["db_type"];
+    } else if (profile === "kingbase" && dbType === "postgres") {
+      dbType = "kingbase" as ConnectionConfig["db_type"];
+    } else if (profile === "vastbase" && dbType === "postgres") {
+      dbType = "vastbase" as ConnectionConfig["db_type"];
+    } else if (profile === "goldendb" && dbType === "mysql") {
+      dbType = "goldendb" as ConnectionConfig["db_type"];
     }
 
     return {