Include git commit hash in SQL extension version

[Copilot]

The absurd_version() SQL function now returns the git commit hash alongside the package version for better build traceability.

Changes

• build.rs: Capture git commit hash at build time via git rev-parse --short HEAD, expose as GIT_COMMIT env var (defaults to "unknown" if git unavailable)
• lib.rs: Update absurd_version() to return format absurd-sqlite/{version} ({commit})
• tests: Update assertion to validate new format

Example

SELECT absurd_version();
-- Returns: absurd-sqlite/0.1.0 (cb550ed)

The commit hash updates automatically on each build, allowing deployed extensions to be traced back to their exact source code state.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>sql extension version should have git commit attached</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes sql extension version should have git commit attached #7

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.