fix(release): use positional shell arg for cask completions

[ryanlewis]

Fixes the completion install broken in v0.4.0. Cuts v0.4.1.

Bug

v0.4.0's cask used shell_parameter_format: arg, so Homebrew invoked things completions --shell=bash. But things completions takes the shell as a positional arg, so Kong rejected the unknown --shell flag (exit 80) and brew install wrote no completion files — with three "Failed to generate … completions" warnings.

(The preflight quarantine fix from #95 worked — the binary executed; exit 80 is our own arg-parse error, not a Gatekeeper block.)

Fix

Drop shell_parameter_format so Homebrew uses its default: a bare positional arg, things completions bash. The GoReleaser docs claim arg means positional, but Homebrew's :arg actually emits --shell=<name>; bare positional is the no-format default.

Generated cask now reads:

generate_completions_from_executable "things", "completions",
  base_name: "things",
  shells: [:bash, :zsh, :fish]

Verification

• goreleaser check ✅; snapshot cask omits shell_parameter_format ✅
• Against the installed v0.4.0 binary: things completions --shell=bash → exit 80 (reproduces the failure); things completions bash → exit 0 emitting complete -C things things; all of bash/zsh/fish exit 0 positionally ✅

After v0.4.1 releases: brew update && brew reinstall ryanlewis/tap/things should write the completion files with no warnings.