feat: implement resumable Claude sessions with background execution (#93)

This comprehensive update adds support for resumable Claude Code sessions that can run in the background and be resumed later. Key improvements include:

Backend enhancements:
- Enhanced ProcessRegistry to track both agent runs and Claude sessions
- Added new Tauri commands: list_running_claude_sessions, get_claude_session_output
- Improved Claude process management with proper session ID extraction and lifecycle handling
- Enhanced cancellation logic with registry-based process killing and fallback mechanisms
- Added live output capture and storage for session persistence

Frontend improvements:
- New RunningClaudeSessions component to display and manage active sessions
- Added streaming state management and session tracking in App component
- Implemented navigation protection when Claude is actively streaming
- Enhanced ClaudeCodeSession component with streaming callbacks and session management

Configuration updates:
- Updated .gitignore to exclude documentation files (AGENTS.md, CLAUDE.md, *_TASK.md)

This feature enables users to start Claude sessions, navigate away while Claude continues processing, and resume sessions later from the Projects view, significantly improving the user experience for long-running AI interactions.

src-tauri/src/main.rs

@@ -21,12 +21,13 @@ use commands::claude::{
     cancel_claude_execution, check_auto_checkpoint, check_claude_version, cleanup_old_checkpoints,
     clear_checkpoint_manager, continue_claude_code, create_checkpoint, execute_claude_code,
     find_claude_md_files, fork_from_checkpoint, get_checkpoint_diff, get_checkpoint_settings,
-    get_checkpoint_state_stats, get_claude_settings, get_project_sessions,
+    get_checkpoint_state_stats, get_claude_session_output, get_claude_settings, get_project_sessions,
     get_recently_modified_files, get_session_timeline, get_system_prompt, list_checkpoints,
-    list_directory_contents, list_projects, load_session_history, open_new_session,
-    read_claude_md_file, restore_checkpoint, resume_claude_code, save_claude_md_file,
-    save_claude_settings, save_system_prompt, search_files, track_checkpoint_message,
-    track_session_messages, update_checkpoint_settings, ClaudeProcessState,
+    list_directory_contents, list_projects, list_running_claude_sessions, load_session_history,
+    open_new_session, read_claude_md_file, restore_checkpoint, resume_claude_code,
+    save_claude_md_file, save_claude_settings, save_system_prompt, search_files,
+    track_checkpoint_message, track_session_messages, update_checkpoint_settings,
+    ClaudeProcessState,
 };
 use commands::mcp::{
     mcp_add, mcp_add_from_claude_desktop, mcp_add_json, mcp_get, mcp_get_server_status, mcp_list,
@@ -114,6 +115,8 @@ fn main() {
             continue_claude_code,
             resume_claude_code,
             cancel_claude_execution,
+            list_running_claude_sessions,
+            get_claude_session_output,
             list_directory_contents,
             search_files,
             create_checkpoint,