Add cask install steps

[MikeMcQuaid]

• Expose structured steps for cask flight phases and API data.
• Prefer steps over matching Ruby flight blocks with warnings.
• Document cask usage and autocorrect simple file preparation.

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[Copilot]

Pull request overview

This PR introduces structured, declarative “install steps” stanzas for casks (covering pre/postflight and uninstall pre/postflight), with supporting artifacts, RuboCop guidance/autocorrection, and documentation so these steps can be represented in JSON API data rather than relying on arbitrary Ruby flight blocks.

Changes:

• Add new cask artifact types and DSL stanzas for preflight_steps, postflight_steps, uninstall_preflight_steps, and uninstall_postflight_steps, and wire them into install/uninstall flows.
• Extend the Cask RuboCop cop to detect simple file-prep flight blocks and autocorrect them into structured *_steps blocks.
• Add fixtures/tests and update the Cask Cookbook to document the new stanzas.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
Library/Homebrew/test/support/fixtures/cask/Casks/with-install-steps.rb	New fixture cask exercising all new *_steps stanzas.
Library/Homebrew/test/rubocops/cask/install_steps_spec.rb	Adds RuboCop cop coverage for autocorrecting simple flight blocks into *_steps.
Library/Homebrew/test/cask/cask_loader/from_api_loader_spec.rb	Ensures API loading covers casks with *_steps stanzas.
Library/Homebrew/test/cask/artifact/install_steps_spec.rb	New artifact/installer integration specs for structured steps and conflict warnings.
Library/Homebrew/sorbet/rbi/dsl/cask/cask.rbi	Adds RBI entries for the new DSL methods.
Library/Homebrew/rubocops/cask/install_steps.rb	Adds autocorrection and auditing for simple file-prep flight blocks.
Library/Homebrew/json_api_postinstall_preflight_postflight_plan.md	Marks the plan item for cask flight steps as completed.
Library/Homebrew/cask/installer.rb	Includes new step artifacts in installer install/uninstall phases (Sorbet casting).
Library/Homebrew/cask/dsl.rb	Adds the new DSL stanzas, step building/normalization, and flight-block conflict handling.
Library/Homebrew/cask/artifact/install_steps.rb	Introduces new AbstractInstallSteps and concrete step artifacts for each phase.
Library/Homebrew/cask/artifact/abstract_artifact.rb	Extends artifact sort ordering to place the new step artifacts appropriately.
Library/Homebrew/cask/artifact.rb	Requires the new install-steps artifact file.
docs/Cask-Cookbook.md	Documents the new *_steps stanzas and adds them to stanza ordering/reference tables.

Files not reviewed (1)

• Library/Homebrew/sorbet/rbi/dsl/cask/cask.rbi: Language not supported

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