Install mise shell completions

[jeremydixon22]

Closes #188.

This generates Bash, Zsh, and Fish completions with the staged mise binary during packaging, rejects empty generated output, and installs each file in the conventional shell-specific location. The existing Fish activation integration remains unchanged.

Verification:

• built mise-bin successfully with makepkg in archlinux:base-devel
• confirmed the resulting package contains all three completion files and the existing Fish activation file
• passed omarchy-release self-test, omarchy-pkgs self-test, and sync-upstream self-test in the Arch environment
• passed package-scoped edge and stable release dry-runs

[greptile-apps]

Greptile Summary

The PR increments the mise-bin package revision and generates Bash, Zsh, and Fish completion scripts using the packaged binary.

• Rejects empty generated completion output during packaging.
• Installs each completion in its conventional shell-specific directory.
• Retains the existing Fish activation integration and package-managed self-update behavior.

Confidence Score: 5/5

The PR appears safe to merge with no actionable correctness, packaging, or security issues identified.

The completion commands and installation paths match the supported shell interfaces, empty output is rejected, architecture-specific builds can execute the corresponding staged binary, and the package revision ensures existing installations receive the new files.

Important Files Changed

Filename	Overview
pkgbuilds/mise-bin/PKGBUILD	Adds guarded generation and conventional installation of completion scripts for three shells, with the required package revision bump.

_{Reviews (1): Last reviewed commit: "Install mise shell completions" | Re-trigger Greptile}