Validate remote and commit options in Bzlmod git_repository needs an incompatibility flag.

### Description of the feature request:

Previously valid git URIs (like `git@gitlab.example.com:company/internal/groups/fancy-bazel-module.git`) are now rejected, and this causes existing, working registries to quit working.

### Which category does this issue belong to?

External Dependency

### What underlying problem are you trying to solve with this feature?

We'd like a way to ensure we retain compatibility with this breaking change on the 9.x.x branch, to ease migration.

### Which operating system are you running Bazel on?

Linux

### What is the output of `bazel info release`?

release 10.0.0-pre.20260902.1

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse HEAD` ?

```text

```

### Have you found anything relevant by searching the web?

_No response_

### Any other information, logs, or outputs that you want to share?

_No response_

Start by locating the Bzlmod git_repository handling for remote and commit validation, then inspect how incompatibility flags are represented elsewhere in Bazel. Done means the requested flag preserves compatibility for previously valid git URIs on the 9.x.x branch and has coverage for the affected validation behavior.

Written by the indexing model from the issue text.