coder(providers): remove retired cursor and copilot providers

Drop both retired providers from BooCoder's provider layer: acp-spawn argv cases, provider-manifest mode blocks + manifest keys, provider-commands maps, the provider-snapshot cursor model-CLI branch (+ orphaned exec/promisify imports), the agent-probe copilot ACP-detect branch, and the now-dead cursor-models module + its test. The PROVIDERS registry array already lacked both. Built-ins unchanged: claude, opencode, goose, qwen, native boocode.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/coder/src/services/__tests__/provider-commands.test.ts

@@ -3,7 +3,7 @@ import { getManifestCommands, mergeCommands, PROVIDER_COMMANDS } from '../provid
 
 describe('provider-commands', () => {
   it('defines commands for every external harness', () => {
-    for (const name of ['claude', 'opencode', 'cursor', 'goose', 'qwen', 'copilot']) {
+    for (const name of ['claude', 'opencode', 'goose', 'qwen']) {
       expect(getManifestCommands(name).length, name).toBeGreaterThan(0);
     }
   });