fix: Improve release tag extraction to avoid issues with some curl version

[theoDep]

This PR is a fix linked to the following issue: #126

Greptile Overview

Greptile Summary

Improved the release tag extraction logic in the installation script to be more robust across different curl versions. The change splits the version detection into two steps: first storing the effective URL from the GitHub redirect, then validating and extracting the tag only if /tag/ is present in the URL. Additionally adds validation to detect if the extraction failed by checking if the version string still contains http.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The changes improve robustness of version detection without introducing new logic or modifying behavior in success cases. The refactoring adds defensive checks that gracefully fall back to the existing "latest" fallback on failure. The changes are well-scoped, backward-compatible, and address a specific compatibility issue with certain curl versions.
• No files require special attention

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