Prioritize sessions from current directory in local command

[wpfleger96]

This PR prioritizes sessions from the current working directory in the local command's session picker, making it faster to find relevant sessions when working across multiple projects.

When running claude-code-transcripts local, users previously saw a flat list of recent sessions from all projects. This became unwieldy for users with many Claude Code sessions across different projects, requiring them to scan through sessions from unrelated work to find what they needed.

• Add find_sessions_for_project() and find_sessions_excluding_project() to filter sessions by directory
• Add encode_path_to_folder_name() to map filesystem paths to Claude's project folder naming scheme
• Modify local command to display sessions in two sections: "Current Project" (up to --limit sessions) and "Other Projects" (up to --limit sessions), with project names shown for the latter
• Extract _should_include_session() helper to reduce code duplication across 4 session-finding functions
• Add comprehensive test coverage for new functions (45 tests passing)