feat(migration): migrate legacy owner data and update config reference handling

- Implemented a migration process to move resources from the legacy owner "default" to the new default owner "local", ensuring no data loss during the transition.
- Updated configuration reference handling to replace legacy `$VAR_`, `$SECRET_`, and `$CONTEXT_` prefixes with mustache-style `{{ vars.name }}`, `{{ secrets.name }}`, and `{{ context.name }}`.
- Enhanced YAML configuration files and scripts to reflect the new mustache syntax, improving consistency across the application.
- Added tests to validate the migration process and ensure proper handling of legacy references.
- Updated documentation to guide users on the new configuration reference format.

AGENTS.md

@@ -120,7 +120,7 @@ Return `{ output, context?, skipRemaining? }`. Do not return `ctx`. Mutations of
 |---|---|
 | `ctx.data` | Step input (trigger payload, previous `output`, or DAG `needs`) |
 | `ctx.context` | Run clipboard (plain object) |
-| `ctx.config` | YAML `config` (secrets already unwrapped from `$SECRET_name`) |
+| `ctx.config` | YAML `config` (mustache refs like `{{ secrets.name }}` already resolved) |
 | `output` | Next step’s `data` |
 | `context` | Next clipboard. Omit to keep incoming |
 
@@ -142,7 +142,7 @@ scripts:
     script: plugin/my-plugin
     config:
       url: http://10.8.0.6:3030/notes
-      token: $SECRET_joplin_api_token
+      token: "{{ secrets.joplin_api_token }}"
 ```
 
 Optional `name` is the display title in the editor and graph (falls back to the script filename). Canonical ref is `plugin/<id>` (`.js` suffix is optional).
@@ -153,4 +153,4 @@ Optional `name` is the display title in the editor and graph (falls back to the
 - Use an id that matches a core script file (`ntfy`, `jsonata`, …).
 - Mismatch folder name and `jerapah-plugin.json` `id` (plugin is disabled).
 - Commit `plugins/.staging-*` or `plugins/*/node_modules/`.
-- Put secrets in `script.js`; use YAML `$SECRET_name` / `$VAR_name`.
+- Put secrets in `script.js`; use YAML `{{ secrets.name }}` / `{{ vars.name }}` (quote if the value starts with `{`).