Reduce setup scripts to core extension/component setup calls

[chubes4]

Finding

Homeboy core owns extension install/setup and component environment detection, while the action still hardcodes extension refresh and generic Composer/npm/pnpm/yarn dependency setup.

Evidence

Action:

• scripts/setup/install-extension.sh
• scripts/setup/detect-runtime-env.sh
• scripts/setup/auto-setup-environment.sh
• action.yml setup steps around homeboy component env

Core upstream issue:

• Add explicit extension refresh/setup mode for CI homeboy#2917

Proposed shape

After core exposes an explicit refresh/setup mode, reduce action setup scripts to platform setup and one core command invocation.

Acceptance criteria

• Extension refresh is not implemented as shell uninstall/install loops.
• Generic dependency install policy moves to extension/core lifecycle where possible.
• Action still supports setup-node/setup-php platform wiring.
• Existing runtime-env outputs remain stable.

Parallelization

Blocked on Extra-Chill/homeboy#2917 for the main cleanup.