chore(tasks): use remote tasks

[rektdeckard]

This patch updates the taskfile to use the remote tasks defined in the index to allow us to update common tasks from a single source of truth.

It also adds some messaging on agent deployment, so that once we go GA, users will get a nice little helper message after bootstrapping an agent template:

To setup and run locally:

    cd <my-app>
    pnpm install
    pnpm build
    pnpm dev

To deploy your agent to LiveKit cloud:

    lk agent create

DO NOT MERGE. This is will be a breaking change for anyone trying to bootstrap this template running livekit-cli<2.5.0. We should wait some time for adoption.

[bcherry]

nice