Add install step write cops

[MikeMcQuaid]

• Make the install-step RuboCops convert simple literal writes now that the write DSL can preserve overwrite semantics explicitly.
• Leave newline-less writes as legacy Ruby because the step DSL appends a trailing newline and autocorrection must not alter file contents.

---

• Have you followed our Contributing guidelines?
• Have you checked for other open Pull Requests for the same change?
• Have you explained what your changes do? Performance claims (e.g. "this is faster") must include Hyperfine benchmarks.
• Have you explained why you'd like these changes included, not just what they do?
• For bug fixes, have you given step-by-step brew commands to reproduce the bug?
• Have you written new tests (excluding integration tests)? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) locally?

---

• AI was used to generate or assist with generating this PR.

OpenAI Codex 5.5 xhigh with local review and testing.

---

[Copilot]

Pull request overview

This PR updates Homebrew’s install-step RuboCops to also recognize and safely autocorrect simple “config file write” patterns inside legacy post_install / flight blocks into the *_steps DSL, now that write can explicitly preserve overwrite behavior. It deliberately avoids autocorrecting writes that don’t end in a newline because the step DSL appends a trailing newline and must not change file contents.

Changes:

• Extend the shared install-steps RuboCop helper to convert simple .write, .atomic_write, and File.write (when the content is a literal string ending with \n) into write ..., overwrite: true.
• Add new formula and cask RuboCop specs covering both the positive autocorrection cases and the “no trailing newline” non-autocorrect cases.
• Update the project plan markdown to mark the PR 5.2 item as completed and document the scope.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/test/rubocops/install_steps_spec.rb	Adds coverage for formula post_install autocorrection to post_install_steps for literal newline-terminated writes (and ensures no autocorrect without trailing newline).
Library/Homebrew/test/rubocops/cask/install_steps_spec.rb	Adds coverage for cask postflight autocorrection to postflight_steps for literal newline-terminated writes (and ensures no autocorrect without trailing newline).
Library/Homebrew/rubocops/shared/install_steps_helper.rb	Implements conversion logic for write/atomic_write/File.write into write step lines with overwrite: true, preserving heredoc formatting.
Library/Homebrew/json_api_postinstall_preflight_postflight_plan.md	Marks the corresponding plan item completed and records the implemented scope/constraints.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.