feat(core): implement TriggerHookAction handler

[kitelev]

Summary

Implements TriggerHookAction handler for ActionInterpreter (Phase 3, Handler 6/8).

Changes

• Added webhookService as 5th constructor parameter to ActionInterpreter
• Implemented triggerHookHandler with full functionality:
  • Takes hookName (required) and payload (optional) parameters
  • Dispatches webhook event via WebhookService.dispatchEvent()
  • Supports payload as JSON string or direct object
  • Includes currentAsset.path in webhook payload
  • Handles errors gracefully with descriptive messages
• Added 7 comprehensive unit tests

Test Coverage

Test Case	Status
Webhook triggering with hookName and payload	✅
Missing hookName validation	✅
WebhookService not initialized error	✅
Object payload (not stringified)	✅
Empty payload handling	✅
Webhook dispatch failure handling	✅
Including filePath from currentAsset	✅

Technical Approach

private triggerHookHandler: ActionHandler = async (def, ctx) => {
  const hookName = def.params['hookName'] as string;
  const payload = def.params['payload'];

  // Dispatch via WebhookService
  await this.webhookService.dispatchEvent({
    event: "property.changed",
    timestamp: new Date().toISOString(),
    filePath: ctx.currentAsset?.path ?? "",
    data: { hookName, payload },
  });

  return { success: true };
};

Test Plan

• All 7 new TriggerHookAction tests pass
• All 60 ActionInterpreter tests pass
• Build passes with no TypeScript errors
• No new lint errors introduced

Closes #1410