Introduce get-version.sh to consistently derive Semantic Versions from Git state across local and CI environments.
Key capabilities:
- Robust SemVer derivation:
    - Supports vMAJOR.MINOR.PATCH[-prerelease] tags.
    - When on a tagged commit: emits the exact SemVer.
    - When ahead of a tag: appends build metadata with the commit count since the tag (e.g., +N).
    - When no tags exist: defaults to 0.0.0+.
    - Optional explicit version argument to override tag discovery when needed.

- CI-friendly and hardened behavior:
    - set -euo pipefail and sanitized IFS for safer shell execution.
    - Works in shallow clones by attempting to fetch tags/unshallow; falls back gracefully.
    - Handles absence of Git or non-repo directories by emitting a safe default and continuing.
    - Emits SemVer and ShortSha to GITHUB_OUTPUT when available for downstream GitHub Actions steps.

- Assembly version stamping (best-effort):
    - Computes AssemblyVersion, AssemblyFileVersion, and AssemblyInformationalVersion.
    - Informational version includes branch and full SHA for traceability.
    - Updates AssemblyInfo.cs files only if Perl is available; otherwise skips with a warning (avoids hard dependency).

- Minimal external dependencies:
    - Requires only Git; Perl is optional and used solely for in-place file updates.