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/agent-probe.ts

@@ -27,15 +27,6 @@ async function detectAcpSupport(agentName: string, installPath: string): Promise
   const transport = PROVIDERS_BY_NAME.get(agentName)?.transport;
   if (transport !== 'acp') return false;
 
-  if (agentName === 'copilot') {
-    try {
-      const { stdout } = await exec(`"${installPath}" --help`, { timeout: 10_000 });
-      return stdout.includes('--acp');
-    } catch {
-      return false;
-    }
-  }
-
   if (agentName === 'qwen') {
     try {
       const { stdout } = await exec(`"${installPath}" --help`, { timeout: 10_000 });