ci(release): generate shell completions in brew formula template

[kengio]

Summary

The release workflow regenerates Formula/onebrain.rb from a heredoc template on every stable tag and PUTs it to onebrain-ai/homebrew-onebrain. This adds the completion-install line to that template:

def install
  bin.install "onebrain"
  generate_completions_from_executable(bin/"onebrain", "completions")
end

So every future release ships a formula whose brew install runs onebrain completions {bash,zsh,fish} and installs the scripts automatically.

Why also here (not just the tap)

The tap formula is auto-regenerated from this template each release. The companion PR homebrew-onebrain#1 patches the live v3.2.19 formula for immediate effect; this PR makes the change durable — without it, the next release would overwrite the tap edit.

Notes

• No version bump: this is release-tooling only, no change to the binary. It takes effect on the next release that cuts a tag.
• The added line is static (no ${...} shell expansion, no #{...} Ruby interpolation), so it passes through the <<FORMULA heredoc verbatim.
• Requires the binary to carry completions <SHELL> — shipped in v3.2.19 (feat(cli): shell completions — hidden completions subcommand + post-init hint (v3.2.19) #61).

🤖 Generated with Claude Code