Extract adapter registry across CLI, server, and UI

Refactor monolithic heartbeat service, AgentConfigForm, and CLI
heartbeat-run into a proper adapter registry pattern. Each adapter
type (process, claude-local, codex-local, http) gets its own module
with server-side execution logic, CLI invocation, and UI config form.
Significantly reduces file sizes and enables adding new adapters
without touching core code.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/adapters/registry.ts

@@ -0,0 +1,22 @@
+import type { ServerAdapterModule } from "./types.js";
+import { claudeLocalAdapter } from "./claude-local/index.js";
+import { codexLocalAdapter } from "./codex-local/index.js";
+import { processAdapter } from "./process/index.js";
+import { httpAdapter } from "./http/index.js";
+
+const adaptersByType = new Map<string, ServerAdapterModule>(
+  [claudeLocalAdapter, codexLocalAdapter, processAdapter, httpAdapter].map((a) => [a.type, a]),
+);
+
+export function getServerAdapter(type: string): ServerAdapterModule {
+  const adapter = adaptersByType.get(type);
+  if (!adapter) {
+    // Fall back to process adapter for unknown types
+    return processAdapter;
+  }
+  return adapter;
+}
+
+export function listAdapterModels(type: string): { id: string; label: string }[] {
+  return adaptersByType.get(type)?.models ?? [];
+}