Add SftpException and SftpPathNotFoundException.Path

[Rob-Hague]

This adds an SftpException which sits between the existing SftpPathNotFoundException/SftpPermissionDeniedException and SshException, and which contains the response code from the SSH_FXP_STATUS packet, along with a default message if one was not provided.

SftpPathNotFoundException also gains a Path property which is populated in cases where it makes sense.

closes#161
closes#567

[Copilot]

Pull Request Overview

This PR introduces a new SftpException class as an intermediate exception type between existing SFTP-specific exceptions (SftpPathNotFoundException, SftpPermissionDeniedException) and the base SshException. The new exception includes a StatusCode property containing the response code from SSH_FXP_STATUS packets, along with default error messages when none are provided. Additionally, SftpPathNotFoundException now includes a Path property that captures the path that wasn't found.

Key changes:

• Introduced SftpException with StatusCode property and default messages for common status codes
• Added Path property to SftpPathNotFoundException to capture the missing path
• Renamed StatusCodes enum to StatusCode and made it public (previously internal)

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
version.json	Bumped version from 2025.0.1 to 2025.1.0 to reflect the new feature
src/Renci.SshNet/Common/SftpException.cs	New exception class with StatusCode property and default message generation
src/Renci.SshNet/Common/SftpPathNotFoundException.cs	Changed to inherit from SftpException, added Path property and path-aware message generation
src/Renci.SshNet/Common/SftpPermissionDeniedException.cs	Changed to inherit from SftpException instead of SshException
src/Renci.SshNet/Sftp/StatusCode.cs	Renamed and made public with added documentation (first 9 status codes)
src/Renci.SshNet/Sftp/StatusCodes.cs	Removed (replaced by StatusCode.cs)
src/Renci.SshNet/Sftp/SftpSession.cs	Updated to use new SftpException and pass path context for better error messages
src/Renci.SshNet/Sftp/Responses/SftpStatusResponse.cs	Updated to use StatusCode enum and enabled nullable reference types
test files	Updated tests to verify new StatusCode property and Path property behavior

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