wiki: add dev-tools section with tmux, screen, and rsync articles

Add three new articles to 03-opensource/dev-tools/:
- tmux: persistent terminal sessions, background jobs, capture-pane
- screen: lightweight alternative, comparison table
- rsync: flags reference, resumable transfers, SSH usage

Update all indexes (SUMMARY, section index, main index, README).
Article count: 28 → 31. Remove tmux from writing backlog.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

03-opensource/index.md

@@ -6,7 +6,9 @@ A curated collection of my favorite open-source tools and privacy-respecting alt
 - [rmlint: Duplicate File Scanning](productivity/rmlint-duplicate-scanning.md)
 
 ## 🛠️ Development Tools
-- *Coming soon*
+- [tmux: Persistent Terminal Sessions](dev-tools/tmux.md)
+- [screen: Simple Persistent Sessions](dev-tools/screen.md)
+- [rsync: Fast, Resumable File Transfers](dev-tools/rsync.md)
 
 ## 🎨 Media & Creative
 - *Coming soon*