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.

.vscode/tasks.json

@@ -4,7 +4,7 @@
     {
       "label": "run",
       "type": "shell",
-      "command": "python3 ${workspaceFolder}/bterminal.py",
+      "command": "python3 ${workspaceFolder}/# v1 removed",
       "group": {
         "kind": "build",
         "isDefault": true