server/coder: working-tree backend changes (pre-existing)

Checkpoint of in-progress backend work present in the tree, not authored this session: auto_name, inference tool-phase/turn, secret_guard, provider-registry, plus a new agent-allowlist test (7 tests, passing).

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

apps/coder/src/services/provider-registry.ts

@@ -24,12 +24,6 @@ export const PROVIDERS: ProviderDef[] = [
     transport: 'native',
     modelSource: 'llama-swap',
   },
-  {
-    name: 'cursor',
-    label: 'Cursor Agent',
-    transport: 'acp',
-    modelSource: 'probe',
-  },
   {
     name: 'opencode',
     label: 'OpenCode',
@@ -59,12 +53,6 @@ export const PROVIDERS: ProviderDef[] = [
     transport: 'acp',
     modelSource: 'probe',
   },
-  {
-    name: 'copilot',
-    label: 'GitHub Copilot',
-    transport: 'acp',
-    modelSource: 'probe',
-  },
 ];
 
 export const PROVIDERS_BY_NAME = new Map(PROVIDERS.map((p) => [p.name, p]));