Fix drupal-rector vendor embedding: strip nested .git, use prefer-dist install
### Problem/Motivation Strip nested .git directories from the dev-main drupal-rector dependency before committing so the real source files are recorded instead of an empty gitlink. This ensures rector's autoloader can resolve DrupalRector\Set\* classes in every per-workspace clone without falling back to a source install that embeds git metadata. ### Work items - Commit(s): [b42ca6b126](https://git.drupalcode.org/project/project_analysis/-/commit/b42ca6b1269e), [856b92f69a](https://git.drupalcode.org/project/project_analysis/-/commit/856b92f69a0d), [ae9d0e7b86](https://git.drupalcode.org/project/project_analysis/-/commit/ae9d0e7b86b5), [96b1724a23](https://git.drupalcode.org/project/project_analysis/-/commit/96b1724a237f), [d84cef440b](https://git.drupalcode.org/project/project_analysis/-/commit/d84cef440b31), [469d218ab0](https://git.drupalcode.org/project/project_analysis/-/commit/469d218ab0d3) ### Credit - Implemented by: @bbrala --- *Filed retroactively as part of the Drupal 12 rector coverage effort. Closed as fixed; credit to be applied to the contributors listed above.* *AI was used extensively to build this work and to file this issue. See [Dries Buytaert: AI-generated Rector rules for Drupal](https://dri.es/ai-generated-rector-rules-for-drupal) and [Björn Brala: Drupal Rector rules are config, not code. Mostly.](https://www.linkedin.com/pulse/drupal-rector-rules-config-code-mostly-bj%C3%B6rn-brala-vfpwe/).*
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