tracking(desktop): coordinate Side Conversation follow-ups

[Phoenix500526]

Problem

Desktop Side Conversations shipped, but the document still contains several
follow-up routes with different owners: panel registration, parent-state
visibility, durable promotion, Review actions and watching, and remote Terminal
restoration. None has a shared coordination tracker, so these documented gaps
can drift or disappear without an explicit disposition.

Desired outcome

Use this issue as the coordination surface for the documented follow-up list.
Each independent lifecycle or authority boundary should move to its own focused
child issue before implementation. This tracker closes when every item is
shipped, explicitly rejected, or represented by a durable child tracker and the
document reflects that status.

Checklist

• Extract the remaining surface switch into a registered tab descriptor model before third-party panel types
• Surface authoritative parent status when the main Session needs input or approval, fails, is interrupted, or completes
• Decide whether an explicit user action may promote a Side Conversation into a visible durable ordinary Session before widening write access
• If promotion is accepted, preserve lineage and workspace/permission semantics and transfer cleanup ownership atomically
• Add commit selection and hunk-level stage/unstage/revert actions to Review
• Add filesystem watching and multi-repository aggregation to Review
• Add remote-host Terminal creation and a restorable route only after Runtime can honestly reattach or recreate it across restart
• Create focused child trackers for accepted slices and keep the document synchronized

Non-goals

• Delivering all follow-ups in one PR
• Making temporary side conversations durable by default
• Reopening completed TUI Side Conversation work
• Bypassing Runtime Host admission, Session identity, or cleanup authority
• Claiming Terminal restoration before the Runtime owns a valid reattach/recreate contract

Documentation

• Side Conversation

[testikun]

The first checklist item now has a focused child issue: #4744 tracks the internal typed Workbar tab-surface descriptor registry, with plugin APIs and Side Conversation/Terminal lifecycle changes explicitly out of scope.

Posted with OpenAI Codex assistance on behalf of @testikun.