Get rid of get/set service inbuilts

[forman]

Summary

• remove the built-in Service.get() query and Service.set() action
• add dedicated store set / set_result protocol messages
• make Python Service generic so service.store preserves Store[T]
• keep store reads/writes on the Store API and service actions/queries for domain behavior
• separate store broadcast suppression from service call context
• fix tracked TS queries so update_task messages before query_result do not hang the promise

Details

• StoreImpl.set() now sends SetMessage and waits for SetResultMessage
• Python server dispatches SetMessage directly against the store
• external Python-side store.set() broadcasts now use SetResultMessage(call_id="store_update")
• user actions still batch multiple store.set() calls into one ActionResultMessage
• get and set are no longer reserved service method names; notify remains reserved
• local TS fallback no longer injects a hidden set action

Checklists

Python package

• pixi run format
• pixi run lint
• pixi run mypy
• pixi run tests
• Updated remotestate-py/CHANGES.md

TypeScript library

• npm run format
• npm run checks
• npm run tests
• npm run build
• Updated remotestate-ts/CHANGES.md

Demo app

• npm run checks
• npm run build
• Updated remotestate-demo/CHANGES.md

[forman]

Ok.