Refactor SSH authentication handling

- Moved SSH utility functions from `ssh_utils.rs` to platform-specific modules.
- Created a new `ssh` module to encapsulate platform-specific implementations for SSH agent management.
- Implemented Unix-specific SSH agent functions in `src/auth/ssh/unix.rs`.
- Implemented Windows-specific SSH agent functions in `src/auth/ssh/windows.rs`.
- Added an unsupported module for platforms that do not support SSH agents in `src/auth/ssh/unsupported.rs`.
- Updated the main authentication module to use the new `ssh` module instead of the deprecated `ssh_utils.rs`.
- Enhanced error handling in the unsupported module to provide clear feedback for unsupported operations.
- Updated the `BGitErrorWorkflowType` enum to include an `Authentication` variant for better error categorization.

Author: rootCircle

src/auth/git_ssh.rs

@@ -2,4 +2,4 @@ pub mod auth_utils;
 pub mod git_auth;
 mod git_http;
 mod git_ssh;
-mod ssh_utils;
+pub mod ssh;

src/auth/mod.rs

@@ -0,0 +1,24 @@
+// Platform-specific SSH implementations
+#[cfg(unix)]
+mod unix;
+#[cfg(not(any(windows, unix)))]
+mod unsupported;
+#[cfg(windows)]
+mod windows;
+
+// Re-export platform-specific functions with a unified interface
+// This follows the same pattern as hook_executor
+#[cfg(unix)]
+pub use self::unix::{
+    add_all_ssh_keys, agent_identities_count, ensure_agent_ready, try_ssh_key_files_directly,
+};
+
+#[cfg(windows)]
+pub use self::windows::{
+    add_all_ssh_keys, agent_identities_count, ensure_agent_ready, try_ssh_key_files_directly,
+};
+
+#[cfg(not(any(windows, unix)))]
+pub use self::unsupported::{
+    add_all_ssh_keys, agent_identities_count, ensure_agent_ready, try_ssh_key_files_directly,
+};