Add devc sync to README

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

Author: DarkaMaul

README.md

@@ -125,10 +125,24 @@ devc shell          Open zsh shell in container
 devc exec CMD       Execute command inside the container
 devc upgrade        Upgrade Claude Code in the container
 devc mount SRC DST  Add a bind mount (host → container)
+devc sync [NAME]    Sync Claude Code sessions from devcontainers to host
 devc template DIR   Copy devcontainer files to directory
 devc self-install   Install devc to ~/.local/bin
 ```
 
+## Session Sync for `/insights`
+
+Claude Code's `/insights` command analyzes your session history, but it only reads from `~/.claude/projects/` on the host. Sessions inside devcontainer volumes are invisible to it.
+
+`devc sync` copies session logs from all devcontainers (running and stopped) to the host so `/insights` can include them:
+
+```bash
+devc sync              # Sync all devcontainers
+devc sync crypto       # Filter by project name (substring match)
+```
+
+Devcontainers are auto-discovered via Docker labels — no need to know container names or IDs. The sync is incremental, so it's safe to run repeatedly.
+
 ## File Sharing
 
 ### VS Code / Cursor