refactor!: rebrand bterminal to agor (agents-orchestrator)

Rename Cargo crates (bterminal-core→agor-core, bterminal-relay→agor-relay),
env vars (BTERMINAL_*→AGOR_*), config paths (~/.config/agor), CSS custom
properties, plugin API object, package names, and all documentation.

BREAKING CHANGE: config/data paths changed from bterminal to agor.

src-tauri/src/groups.rs

@@ -1,5 +1,5 @@
 // Project group configuration
-// Reads/writes ~/.config/bterminal/groups.json
+// Reads/writes ~/.config/agor/groups.json
 // Path configurable via init() for test isolation.
 
 use serde::{Deserialize, Serialize};
@@ -99,7 +99,7 @@ fn config_path() -> PathBuf {
     CONFIG_PATH.get().cloned().unwrap_or_else(|| {
         dirs::config_dir()
             .unwrap_or_else(|| PathBuf::from("."))
-            .join("bterminal")
+            .join("agor")
             .join("groups.json")
     })
 }