Add `werma version` command with build info

[ArLeyar]

Description

Currently werma --version shows just the version number. A dedicated werma version command could show richer build info (git commit, build date, Rust version) which is helpful for debugging.

What needs to happen

1. Add a werma version subcommand
2. Include: version, git SHA (short), build date, Rust version
3. Use compile-time environment variables (VERGEN or built crate, or manual env!())

Example output

werma 0.48.1
  commit:  a3105f8
  built:   2026-03-30
  rustc:   1.88.0

Acceptance Criteria

• werma version prints version + build metadata
• Build info embedded at compile time (not runtime)