chore: remove abandoned Pulse+ references and old changelog

- Remove old RC changelog (v4.15.0-rc.6)
- Update .gitignore comment for experimental features
- Clean up repo of unused files

Pulse+ / cloud relay feature was abandoned, no telemetry or cloud
features are part of Pulse. All monitoring stays local.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -131,7 +131,7 @@ AGENT_METRICS_*.md
 tmp_*.py
 tmp_*.sh
 
-# Cloud relay development (separate repo)
+# Experimental/abandoned features (not part of main project)
 cloud-relay/
 scripts/agent/
 docs/internal/

CHANGELOG_v4.15.0-rc.6.md

@@ -1,48 +0,0 @@
-## Note for RC versions
-This is a pre-release version for testing. Consider backing up your Pulse configuration before updating.
-
-## What's Changed
-
-### Improvements
-- **Enhanced diagnostics export** - Now includes critical troubleshooting data:
-  - Backend diagnostics when available
-  - Node online/offline status
-  - Physical disks information  
-  - ZFS pool health details
-  - Alert configuration
-  - Connection health metrics
-  - Helps identify issues like missing storage, timeout errors, and threshold save problems
-
-### Documentation  
-- Added GitHub issue templates with diagnostics export instructions
-- Templates guide users to provide better information when reporting issues
-
-### Why this matters
-This release significantly improves troubleshooting capabilities. The enhanced diagnostics export will help identify and resolve issues like:
-- Storage only showing from one node (when others timeout)
-- 504 errors when saving thresholds
-- Missing physical disk information
-- Alert configuration problems
-
-## Testing v4.15.0-rc.6
-
-**Install script:**
-```bash
-curl -fsSL https://raw.githubusercontent.com/rcourtman/Pulse/main/install.sh | bash -s -- --version v4.15.0-rc.6
-```
-
-**Docker:**
-```bash
-docker pull rcourtman/pulse:v4.15.0-rc.6
-docker run -d --name pulse -p 7655:7655 -v pulse-data:/etc/pulse rcourtman/pulse:v4.15.0-rc.6
-```
-
-## How to provide feedback
-If you're still experiencing issues after updating:
-1. Go to Settings → Diagnostics tab
-2. Click "Run Diagnostics" first
-3. Then click "Export for GitHub" 
-4. Attach the exported file to your issue report
-
-## Downloads
-Pre-built binaries available below for linux-amd64, linux-arm64, and linux-armv7.