Update action.mdx: mark execute as deprecated, add target binding docs, platform comparison, and cross-reference validation section

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

content/docs/references/ui/action.mdx

@@ -37,8 +37,8 @@ const result = Action.parse(data);
 | **locations** | `Enum<'list_toolbar' \| 'list_item' \| 'record_header' \| 'record_more' \| 'record_related' \| 'global_nav'>[]` | optional | Locations where this action is visible |
 | **component** | `Enum<'action:button' \| 'action:icon' \| 'action:menu' \| 'action:group'>` | optional | Visual component override |
 | **type** | `Enum<'script' \| 'url' \| 'modal' \| 'flow' \| 'api'>` | ✅ | Action functionality type |
-| **target** | `string` | optional | URL, Script Name, Flow ID, or API Endpoint |
-| **execute** | `string` | optional | Legacy execution logic |
+| **target** | `string` | conditional | URL, Script Name, Flow ID, Modal/Page Name, or API Endpoint. **Required** for `url`, `flow`, `modal`, and `api` types; recommended for `script`. |
+| **execute** | `string` | optional | ⚠️ **Deprecated** — Use `target` instead. Auto-migrated to `target` during parsing. Will be removed in a future version. |
 | **params** | `Object[]` | optional | Input parameters required from user |
 | **variant** | `Enum<'primary' \| 'secondary' \| 'danger' \| 'ghost' \| 'link'>` | optional | Button visual variant for styling (primary = highlighted, danger = destructive, ghost = transparent) |
 | **confirmText** | `string \| Object` | optional | Confirmation message before execution |
@@ -51,6 +51,51 @@ const result = Action.parse(data);
 | **timeout** | `number` | optional | Maximum execution time in milliseconds for the action |
 | **aria** | `Object` | optional | ARIA accessibility attributes |
 
+### Target Binding Rules
+
+The `target` field is the canonical way to bind an action to its handler:
+
+| Action Type | target | Description |
+| :--- | :--- | :--- |
+| `script` | Recommended | Function name to invoke (e.g. `completeTask`) |
+| `url` | **Required** | URL to navigate to |
+| `flow` | **Required** | Flow name to invoke (validated against defined flows) |
+| `modal` | **Required** | Page/modal name to open (validated against defined pages) |
+| `api` | **Required** | API endpoint to call |
+
+### Examples
+
+```typescript
+// Script action with handler target
+const action: Action = {
+  name: 'complete_task',
+  label: 'Mark Complete',
+  type: 'script',
+  target: 'completeTask',      // ← references a registered handler function
+  locations: ['record_header'],
+  refreshAfter: true,
+};
+
+// Flow action
+const flowAction: Action = {
+  name: 'convert_lead',
+  label: 'Convert Lead',
+  type: 'flow',
+  target: 'lead_conversion',   // ← must match a defined flow name
+};
+
+// Modal action
+const modalAction: Action = {
+  name: 'defer_task',
+  label: 'Defer Task',
+  type: 'modal',
+  target: 'defer_task_modal',  // ← must match a defined page name
+};
+```
+
+<Callout type="warn">
+**Migration Note:** The `execute` field is deprecated. If `execute` is provided without `target`, it is automatically migrated to `target` during schema parsing. Always use `target` in new code.
+</Callout>
 
 ---
 
@@ -69,3 +114,25 @@ const result = Action.parse(data);
 
 ---
 
+## Cross-Reference Validation
+
+`defineStack()` validates action cross-references at build time:
+
+- **`type: 'flow'`** — `target` is checked against the `flows[]` collection (when flows are defined).
+- **`type: 'modal'`** — `target` is checked against the `pages[]` collection (when pages are defined).
+
+When the target collection is empty, validation is skipped because referenced items may come from plugins.
+
+---
+
+## Platform Comparison
+
+| Capability | ObjectStack | Salesforce | ServiceNow | Power Platform |
+| :--- | :--- | :--- | :--- | :--- |
+| **Declarative actions** | `ActionSchema` with `target` binding | Lightning Actions (Quick Actions) | UI Actions / Client Scripts | Power Fx `OnSelect` |
+| **Action types** | `script`, `url`, `modal`, `flow`, `api` | URL, Flow, LWC, Visualforce | Client Script, UI Policy, Flow | Navigate, Patch, Launch |
+| **Handler binding** | `target` string → `engine.registerAction()` | Apex Controller `@AuraEnabled` | Script Include + GlideAjax | Power Automate Cloud Flow |
+| **Cross-ref validation** | Build-time (`defineStack`) | Deploy-time (Metadata API) | Update Set validation | Solution Checker |
+| **Modal integration** | `type: 'modal'` + page name target | `lightning:overlayLibrary` | GlideModal / GlideDialogWindow | `Navigate(Screen)` |
+| **Bulk operations** | `bulkEnabled` + `locations: ['list_toolbar']` | List Button + Mass Quick Action | List v3 Actions | Gallery `OnSelect` multi |
+