Fix worktree recreation when directory exists without git metadata

[LSRCT]

Summary

• Fix is_worktree_properly_set_up to return Ok(false) instead of throwing InvalidPath error when a worktree directory exists but has no corresponding .git/worktrees/ metadata entry
• This allows the recreation flow to clean up and reinitialize the worktree properly

Problem

When a workspace directory exists on disk but lacks git worktree metadata (no .git file, no entry in the repo's .git/worktrees/), the function was throwing an error:

Failed to recreate worktree before log normalization for workspace X: Invalid path: Invalid worktree path

This prevented recovery and blocked operations like log normalization.

Solution

Changed the logic from:

let worktree_name = Self::find_worktree_git_internal_name(&repo_path, &worktree_path)?
    .ok_or_else(|| WorktreeError::InvalidPath("Invalid worktree path".to_string()))?;

To:

let Some(worktree_name) = Self::find_worktree_git_internal_name(&repo_path, &worktree_path)? else {
    // Directory exists but not registered in git metadata - needs recreation
    return Ok(false);
};

Now when a directory exists without git metadata, the function returns Ok(false) which triggers the recreation flow to clean up and create a fresh worktree.

Test plan

• [x] cargo check -p services passes
• [ ] Verify worktree recreation works for workspaces with orphaned directories

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