feat(workflows): migrate legacy workflows and enhance example handling

- Migrated legacy workflow files from `packages/server/workflows/` to `packages/server/data/workflows/` when the new store is empty.
- Introduced new API endpoints to list and retrieve example workflows.
- Added a dialog component for selecting example workflows when creating new workflows.
- Updated workflow paths and configurations to reflect the new structure.
- Enhanced the README and AGENTS.md documentation to clarify workflow management and usage.

Co-authored-by: Nasyarobby Putra <nasyarobby@gmail.com>

packages/server/paths.js

@@ -3,8 +3,12 @@ import { fileURLToPath } from "url";
 
 export const SERVER_ROOT = path.dirname(fileURLToPath(import.meta.url));
 export const SCRIPTS_DIR = path.join(SERVER_ROOT, "scripts");
-export const WORKFLOWS_DIR = path.join(SERVER_ROOT, "workflows");
 export const DATA_DIR = path.join(SERVER_ROOT, "data");
+/** Live instance workflows (not shipped in git). Override for tests. */
+export const WORKFLOWS_DIR =
+  process.env.JFLOW_WORKFLOWS_DIR ?? path.join(DATA_DIR, "workflows");
+/** Pre-0.1 layout; used only for one-shot migrate into WORKFLOWS_DIR. */
+export const LEGACY_WORKFLOWS_DIR = path.join(SERVER_ROOT, "workflows");
 /** User plugins (repo-root /plugins, outside the pnpm workspace). */
 export const PLUGINS_DIR =
   process.env.JFLOW_PLUGINS_DIR ??
@@ -14,5 +18,10 @@ export const EXAMPLE_PLUGINS_DIR = path.resolve(
   SERVER_ROOT,
   "../../examples/plugins",
 );
+/** Example workflow YAML presets (not loaded by the runner). */
+export const EXAMPLE_WORKFLOWS_DIR = path.resolve(
+  SERVER_ROOT,
+  "../../examples/workflows",
+);
 export const LOGS_DIR = path.join(SERVER_ROOT, "logs");
 export const WEB_DIST = path.resolve(SERVER_ROOT, "../web/dist");