Jujutsu does not have SHA-1 collision detection

### Summary
Jujutsu 0.28.0 and earlier rely on versions of gitoxide that use SHA-1 hash implementations without any collision detection, leaving them vulnerable to hash collision attacks.

### Details
This is a result of the underlying [CVE-2025-31130 / GHSA-2frx-2596-x5r6](https://github.com/GitoxideLabs/gitoxide/security/advisories/GHSA-2frx-2596-x5r6) vulnerability in the gitoxide library Jujutsu uses to interact with Git repositories; see that advisory for technical details. This separate advisory is being issued due to the downstream impact on users of Jujutsu.

### Impact
An attacker with the ability to mount a collision attack on SHA-1 like the [SHAttered](https://shattered.io/) or [SHA-1 is a Shambles](https://sha-mbles.github.io/) attacks could create two distinct Git objects with the same hash. This is becoming increasingly affordable for well‐resourced attackers, with the Shambles researchers in 2020 estimating $45k for a chosen‐prefix collision or $11k for a classical collision, and projecting less than $10k for a chosen‐prefix collision by 2025. The result could be used to disguise malicious repository contents, or potentially exploit assumptions in Jujutsu’s logic to cause further vulnerabilities.