Evaluate removing superdeck_cli in favor of documented builder setup

[leoafarias]

Summary

Evaluate whether SuperDeck should remove superdeck_cli and rely on documented superdeck_builder setup instead. This is intentionally deferred from the plugin PR so that PR can stay focused on the Mermaid/PDF plugin work.

Context

The CLI currently wraps deck build/watch, setup guidance, pubspec asset patching, macOS entitlement patching, and build plugin registration. The runtime itself does not need the CLI; generated deck output and generated assets live under .superdeck/.

Questions to resolve

• Can superdeck_builder be the primary supported build surface without a CLI wrapper?
• Where should manual setup docs live for pubspec.yaml assets and macOS entitlements?
• Should the demo include a small reusable tool/build_deck.dart template for direct builder usage?
• What replaces current CI/Firebase/demo commands that run dart run superdeck_cli:main build?

Setup details to document

• Add .superdeck/ to flutter.assets in pubspec.yaml.
• Keep macOS entitlements documented for debug/release where local file access, network client/server, downloads, and JIT are needed.
• Explain that build plugins such as Mermaid generate local files under .superdeck/ and the Flutter app bundles those files for release/web builds.

Acceptance criteria

• A decision on whether to remove, shrink, or keep superdeck_cli.
• A replacement build/watch workflow for demo, CI, docs, and plugin authoring.
• Documentation for manual setup, including pubspec assets and macOS entitlements.