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>

cli/src/adapters/index.ts

@@ -0,0 +1,2 @@
+export { getCLIAdapter } from "./registry.js";
+export type { CLIAdapterModule } from "./types.js";