Fix bare worktree identity in worktree switcher

[saberoueslati]

Context

This fixes #54830, where switching to an existing git worktree in a bare shared-dir layout caused Zed to treat the linked worktree directory as the project root. In a layout like monty/.bare, monty/main, and monty/feature-a, the repository metadata fell back to the linked checkout path because original_repo_path_from_common_dir only recognized .git common dirs. That made the title bar show the project as feature-a and the worktree label as main.

The fix teaches original_repo_path(...) to recognize linked worktrees whose shared git dir is bare and stored under common_dir/worktrees/.... In that case, it now resolves the original repo path to common_dir.parent(), which matches how WorktreeStore already groups these worktrees. I also added targeted regression coverage for both the path resolution helper and the bare-layout project scan path.

Closes #54830

Video of the manual test below :

Screencast.from.2026-04-28.01-31-39.webm

How to Review

• crates/git/src/repository.rs: Updates original repo path resolution so linked worktrees backed by a bare shared git dir resolve to the shared project root instead of the linked checkout path. Adds unit coverage for normal repos, non-bare linked worktrees, bare linked worktrees, and plain bare repos.
• crates/project/tests/integration/project_tests.rs: Adds an integration regression test for the .bare + main + feature-a layout and verifies that scanning feature-a produces repository metadata rooted at monty while still identifying the checkout as a linked worktree.

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• Fixed git worktree switching to preserve the shared project identity for repositories using a bare .bare worktree layout