Version 2.0.0-beta.6

[crvernon]

This pull request updates documentation and example manifests to focus on the Demeter land-use/land-cover change (LULCC) model as the canonical example for Scalable v2.0.0, while removing references to the model emulation subsystem and related configuration. It also introduces a new optional dependency group for easier installation of all features. The changes improve clarity for new users, unify documentation around the Demeter example, and streamline installation and configuration.

Major documentation and manifest updates:

Demeter as the canonical example:

• Added a new comprehensive Demeter example manifest (docs/examples/scalable.demeter.yaml) covering local, HPC, Kubernetes, and AWS targets, referenced by all tutorials and notebooks.
• Updated existing example manifests (scalable.aws.yaml, scalable.gke.yaml) to use Demeter instead of previous energy model/GCAM examples, with new component names, images, and tags. [1] [2] [3] [4]

Removal of model emulation documentation:

• Deleted the dedicated model emulation documentation page (docs/emulation.rst).
• Removed emulation-related sections, CLI examples, and configuration variables from README.md and other docs. [1] [2] [3] [4]

Installation and getting started improvements:

Simplified installation:

• Introduced a new [all] optional dependency group, allowing users to install all optional features with pip install scalable[all]. Updated installation instructions in README.md and docs/getting_started.rst accordingly. [1] [2]

Beginner guidance and quick start:

• Updated beginner path recommendations and installation examples to reference the new Demeter example and tasks. [1] [2] [3]

Other documentation refinements:

AI assistants and artifact storage:

• Clarified and streamlined AI assistant and artifact storage documentation, removing phase/version references and outdated model lists. [1] [2] [3]

Cloud provider documentation:

• Updated GCP provider documentation to remove phase/version references and clarify current capabilities.