fix: Resolve Windows test failures - local path detection and Git path separators

This commit fixes two critical cross-platform issues causing test failures on Windows:

## Problem 1: Local Path Detection Fails on Windows
The preflight health check logic in split.rs and sync.rs only recognized Unix-style
paths (/, ./, ../), causing Windows paths like C:\Users\... to be incorrectly
identified as remote URLs. This triggered unnecessary SSH preflight checks that
failed in test environments.

### Solution:
- Added is_local_path() helper function that properly detects local paths on both
  Unix and Windows
- Uses Path::is_absolute() which works cross-platform
- Handles Windows-specific cases: drive letters (C:\), UNC paths (\\server\share)
- Applied to both split.rs:114 and sync.rs:156

## Problem 2: Git Commands Receive Windows Backslashes
Git always expects forward slashes in path specifications (e.g., "HEAD:src/file.rs"),
even on Windows. However, Path::display() outputs backslashes on Windows, causing
git cat-file and git ls-tree commands to fail with "missing" file errors.

### Solution:
- Added path_to_git_format() helper in system_git_ops.rs that converts backslashes
  to forward slashes on Windows
- Applied to all Git tree spec operations:
  - read_files_bulk() at line 766 (bulk file reading)
  - get_file_at_commit() at line 175 (single file reads)
  - list_files_at_commit() at line 356 (tree listing)

## Impact:
- Fixes 16 failing integration tests on Windows (all test_split::*, test_sync::*,
  test_workflow::* tests)
- Fixes 1 failing unit test (test_collect_tree_files_with_bulk)
- No behavior change on Unix/Linux/macOS
- Tests pass locally on macOS, should now pass on Windows CI runners

Closes the Windows test failure blocking issue.

Author: loadingalias

src/commands/split.rs

@@ -1,5 +1,6 @@
 use std::env;
 use std::io::{self, Write};
+use std::path::Path;
 
 use crate::commands::doctor;
 use crate::core::config::RailConfig;
@@ -9,6 +10,50 @@ use crate::core::split::{SplitConfig, Splitter};
 use crate::ui::progress::{FileProgress, MultiProgress};
 use rayon::prelude::*;
 
+/// Check if a path is a local filesystem path (not a remote URL)
+///
+/// Returns true for:
+/// - Absolute paths on Unix: /path/to/repo
+/// - Absolute paths on Windows: C:\path\to\repo or C:/path/to/repo
+/// - Relative paths: ./path or ../path
+/// - UNC paths on Windows: \\server\share
+///
+/// Returns false for:
+/// - SSH URLs: [email protected]:user/repo.git
+/// - HTTPS URLs: <https://github.com/user/repo.git>
+fn is_local_path(path: &str) -> bool {
+  let p = Path::new(path);
+
+  // Check for relative paths
+  if path.starts_with("./") || path.starts_with("../") {
+    return true;
+  }
+
+  // Check for absolute paths (works on both Unix and Windows)
+  if p.is_absolute() {
+    return true;
+  }
+
+  // Check for Windows UNC paths (\\server\share)
+  #[cfg(target_os = "windows")]
+  if path.starts_with("\\\\") {
+    return true;
+  }
+
+  // If it contains :// it's a URL
+  if path.contains("://") {
+    return false;
+  }
+
+  // If it contains @ it's likely an SSH URL ([email protected]:user/repo.git)
+  if path.contains('@') {
+    return false;
+  }
+
+  // Default to false for safety (require preflight checks)
+  false
+}
+
 /// Prompt user for confirmation
 fn prompt_for_confirmation(message: &str) -> RailResult<bool> {
   print!("\n{}: ", message);
@@ -66,9 +111,7 @@ pub fn run_split(
   }
 
   // Check if all remotes are local paths (skip SSH checks for local testing)
-  let all_local = crates_to_split_check
-    .iter()
-    .all(|s| s.remote.starts_with('/') || s.remote.starts_with("./") || s.remote.starts_with("../"));
+  let all_local = crates_to_split_check.iter().all(|s| is_local_path(&s.remote));
 
   // Run preflight health checks before proceeding (skip for local-only operations)
   if !json && apply && !all_local {

src/commands/sync.rs

@@ -1,4 +1,5 @@
 use std::env;
+use std::path::Path;
 
 use crate::commands::doctor;
 use crate::core::config::RailConfig;
@@ -9,6 +10,50 @@ use crate::core::sync::{SyncConfig, SyncDirection, SyncEngine, SyncResult};
 use crate::ui::progress::{FileProgress, MultiProgress};
 use rayon::prelude::*;
 
+/// Check if a path is a local filesystem path (not a remote URL)
+///
+/// Returns true for:
+/// - Absolute paths on Unix: /path/to/repo
+/// - Absolute paths on Windows: C:\path\to\repo or C:/path/to/repo
+/// - Relative paths: ./path or ../path
+/// - UNC paths on Windows: \\server\share
+///
+/// Returns false for:
+/// - SSH URLs: [email protected]:user/repo.git
+/// - HTTPS URLs: <https://github.com/user/repo.git>
+fn is_local_path(path: &str) -> bool {
+  let p = Path::new(path);
+
+  // Check for relative paths
+  if path.starts_with("./") || path.starts_with("../") {
+    return true;
+  }
+
+  // Check for absolute paths (works on both Unix and Windows)
+  if p.is_absolute() {
+    return true;
+  }
+
+  // Check for Windows UNC paths (\\server\share)
+  #[cfg(target_os = "windows")]
+  if path.starts_with("\\\\") {
+    return true;
+  }
+
+  // If it contains :// it's a URL
+  if path.contains("://") {
+    return false;
+  }
+
+  // If it contains @ it's likely an SSH URL ([email protected]:user/repo.git)
+  if path.contains('@') {
+    return false;
+  }
+
+  // Default to false for safety (require preflight checks)
+  false
+}
+
 /// Sync command parameters
 pub struct SyncParams {
   pub crate_name: Option<String>,
@@ -108,9 +153,7 @@ fn run_sync_impl(params: SyncParams) -> RailResult<()> {
   }
 
   // Check if all remotes are local paths (skip SSH checks for local testing)
-  let all_local = crates_to_sync_check
-    .iter()
-    .all(|s| s.remote.starts_with('/') || s.remote.starts_with("./") || s.remote.starts_with("../"));
+  let all_local = crates_to_sync_check.iter().all(|s| is_local_path(&s.remote));
 
   // Run preflight health checks before proceeding (skip for local-only operations)
   if !json && apply && !all_local {

src/core/vcs/system_git_ops.rs

@@ -18,6 +18,23 @@ impl SystemGit {
     }
   }
 
+  /// Convert a path to Git format (always forward slashes)
+  ///
+  /// Git expects paths with forward slashes, even on Windows.
+  /// This function converts backslashes to forward slashes for use in Git commands.
+  fn path_to_git_format(&self, path: &Path) -> String {
+    // On Windows, convert backslashes to forward slashes
+    // On Unix, this is a no-op since paths already use forward slashes
+    #[cfg(target_os = "windows")]
+    {
+      path.to_string_lossy().replace('\\', "/")
+    }
+    #[cfg(not(target_os = "windows"))]
+    {
+      path.to_string_lossy().to_string()
+    }
+  }
+
   /// Get commit history from HEAD with optional limit
   ///
   /// Returns commits in reverse chronological order (newest first).
@@ -153,8 +170,9 @@ impl SystemGit {
   #[allow(dead_code)]
   pub fn get_file_at_commit(&self, commit_sha: &str, path: &Path) -> RailResult<Option<Vec<u8>>> {
     let relative_path = self.normalize_path(path);
+    let git_path = self.path_to_git_format(relative_path);
 
-    let spec = format!("{}:{}", commit_sha, relative_path.display());
+    let spec = format!("{}:{}", commit_sha, git_path);
 
     let output = self
       .git_cmd()
@@ -334,7 +352,8 @@ impl SystemGit {
     let spec = if path.as_os_str().is_empty() {
       commit_sha.to_string()
     } else {
-      format!("{}:{}", commit_sha, path.display())
+      let git_path = self.path_to_git_format(path);
+      format!("{}:{}", commit_sha, git_path)
     };
 
     let output = self
@@ -746,7 +765,8 @@ impl SystemGit {
     // Write all requests to stdin
     for (commit_sha, path) in items {
       let relative_path = self.normalize_path(path);
-      let spec = format!("{}:{}\n", commit_sha, relative_path.display());
+      let git_path = self.path_to_git_format(relative_path);
+      let spec = format!("{}:{}\n", commit_sha, git_path);
       stdin
         .write_all(spec.as_bytes())
         .context("Failed to write to git cat-file stdin")?;