feat(ai-foundry): add TypeSpec for Foundry Routines feature

- Add src/routines/models.tsp with RoutineTrigger (schedule/timer/github_issue),
  RoutineAction (invoke_agent_responses_api / invoke_agent_invocations_api),
  RoutineDispatchPayload, RoutineRunDto, and RoutineRunsResponse models
- Add src/routines/routes.tsp with createOrUpdate, get, list, delete,
  dispatch, dispatchAsync, and listRuns operations
- Add routines_v1_preview feature flag to FoundryFeaturesOptInKeys
- Wire up main.tsp import
- Regenerate openapi3 output

Author: lindazqli

specification/ai-foundry/data-plane/Foundry/main.tsp

@@ -20,6 +20,7 @@ import "./src/openai-evaluations/routes.tsp";
 import "./src/openai-finetuning/routes.tsp";
 import "./src/openai-responses/routes.tsp";
 import "./src/red-teams/routes.tsp";
+import "./src/routines/routes.tsp";
 import "./src/schedules/routes.tsp";
 import "./src/skills/routes.tsp";
 import "./src/toolboxes/routes.tsp";