v2.2.5-beta0 - Subagent context and compression state improvements

What's Changed

• Added experimental subagent support:

"experimental": { "allowSubAgents": true }

• /undo properly undoes (?) compressions done in the undone messages
• Bumped package metadata to 2.2.5-beta0.

Full Changelog: v2.2.3-beta0...v2.2.5-beta0