Implement unified system widget with NixOS info, CPU, RAM, and Storage

- Create NixOS collector for version and active users detection
- Add SystemWidget combining all system information in TODO.md layout
- Replace separate CPU/Memory widgets with unified system display
- Add tree structure for storage with drive temperature/wear info
- Support NixOS version, active users, load averages, memory usage
- Follow exact decimal formatting from specification

CLAUDE.md

@@ -6,52 +6,65 @@ A high-performance Rust-based TUI dashboard for monitoring CMTEC infrastructure.
 
 ## Implementation Strategy
 
-### Next Phase: Systemd Collector Optimization (Based on TODO.md)
+### Current Implementation Status
 
-**Current Status**: Reverted to working baseline (commit 245e546) after optimization broke service discovery.
+**Systemd Collector Optimization - COMPLETED** ✅
 
-**Planned Implementation Steps** (step-by-step to avoid breaking functionality):
+All phases successfully implemented:
+- ✅ **Phase 1**: Exact name filtering implemented
+- ✅ **Phase 2**: User service collection removed  
+- ✅ **Phase 3**: Wildcard pattern support added
+- ✅ **Phase 4**: Status caching and systemctl call optimization completed
+- ❌ **Phase 5**: Skipped (would increase systemctl calls vs current caching)
 
-**Phase 1: Exact Name Filtering**
-- Replace `contains()` matching with exact name matching for service filters
-- Change `service_name.contains(pattern) || pattern.contains(service_name)` to `service_name == pattern`
-- Test: Ensure cmbox remains visible with exact service names in config
-- Commit and test after each change
+**Performance Results:**
+- Reduced from ~21 systemctl calls to 1 call every 10 seconds (configurable)
+- Fixed RwLock deadlock issues
+- Removed hardcoded discovery intervals
 
-**Phase 2: Remove User Service Collection** 
-- Remove all `sudo -u` systemctl commands for user services
-- Remove user_unit_files_output and user_units_output logic
-- Keep only system service discovery via `systemctl list-units --type=service`
-- Test: Verify system services still discovered correctly
+### Next Priority: System Panel Enhancement (Based on TODO.md)
 
-**Phase 3: Add Wildcard Support**
-- Implement glob pattern matching for service filters
-- Support patterns like "nginx*" to match "nginx", "nginx-config-reload", etc.
-- Use fnmatch or similar for wildcard expansion
-- Test: Verify patterns work as expected
+**Target Layout:**
+```
+NixOS:
+Version: xxxxxxxxxx
+Active users: cm, simon
+CPU:
+● Load: 0.02 0.31 0.86 • 3000 MHz
+RAM:
+● Usage: 33% 2.6GB/7.6GB  
+● /tmp: 0% 0B/2.0GB  
+Storage:  
+● root (Single):  
+ ├─ ● nvme0n1 Temp: 40C Wear: 4%  
+ └─ ● 8% 75.0GB/906.2GB
+```
 
-**Phase 4: Optimize systemctl Calls**
-- Cache service status information during discovery
-- Eliminate redundant `systemctl is-active` and `systemctl show` calls per service
-- Parse status from `systemctl list-units` output directly
-- Test: Ensure performance improvement without functionality loss
+**Implementation Tasks:**
+1. **NixOS Version Display**
+   - Collect system version information
+   - Show timestamp/version for latest nixos rebuild
 
-**Phase 5: Include-Only Discovery**
-- Remove auto-discovery of all services
-- Only check services explicitly listed in service_name_filters
-- Skip systemctl discovery entirely, use configured list directly
-- Test: Verify only configured services are monitored
+2. **Active Users Display**
+   - Implement user session detection
+   - Show currently logged in/active users
 
-**Critical Requirements:**
-- Each phase must be tested independently
-- cmbox must remain visible in dashboard after each change
-- No functionality regressions allowed
-- Commit each phase separately with descriptive messages
+3. **System Widget Layout Update**
+   - Update dashboard to match new layout specification
+   - Integrate NixOS version and user information
 
-**Rollback Strategy:**
-- If any phase breaks functionality, immediately revert that specific commit
-- Do not attempt to "fix forward" - revert and redesign the problematic step
-- Each phase should be atomic and independently revertible
+### Future Priorities
+
+**Keyboard Navigation (Dashboard):**
+- Change host switching to "Shift-Tab"
+- Add panel navigation with "Tab"
+- Add scrolling support for overflow content
+
+**Remote Execution (Agent/Dashboard):**
+- Dynamic statusbar with context shortcuts
+- Remote nixos rebuild commands
+- Service start/stop/restart controls
+- Backup trigger functionality
 
 ## Core Architecture Principles - CRITICAL