Plan: distribute change-fabric via Homebrew

[pstaylor-patrick]

Planning doc only, nothing implemented. Recommends:

• A custom tap (pstaylor-patrick/homebrew-pst), not homebrew-core: this toolkit fails core's notability bar and its whole job is mutating files outside the Cellar (~/.claude/, ~/.pi/, ~/.config/opencode/), which core rejects.
• A formula that vendors the repo into libexec and shells out to the existing install.rb from post_install, run on both install and every upgrade, since ~/.claude/skills symlinks point into the Cellar and need re-pointing after each Cellar move.
• A stable formula tracking skills/v* tags, with a head block for main; no formula-level pre-release channel (the schema's -alpha.N/-beta.N convention is a separate axis from how the toolkit itself ships).
• A new tag-triggered GitHub Actions workflow using brew bump-formula-pr against the tap with a scoped PAT, kept separate from the existing tag-on-version.yml.
• Explicit punts: homebrew-core, a pre-release formula channel, an automated brew uninstall teardown, a GitHub App, bottling, gem/Node bundling.

Full reasoning and file citations in docs/homebrew-distribution-plan.md.