Fleet UI Phase 4: Brain terminal pinning

[Wirasm]

Phase 4: Brain Terminal Pinning

Part of #562 (Fleet UI Epic)

PRD: .claude/PRPs/prds/fleet-ui-honryu-visibility.prd.md — Phase 4

What

Pin the brain (Honryū) terminal in the Control pane grid when fleet is active. The Tōryō always sees what the brain is doing.

Why

The brain is the fleet coordinator. Having its terminal always visible alongside worker terminals gives the Tōryō real-time oversight of fleet coordination.

Scope

4.1 Brain Pane Slot

• Add "pinned" concept to PaneGrid — slot 0 (top-left) locks to brain session when fleet active
• auto_populate(): detect brain session (branch == "honryu"), pin to slot 0
• Pinned slot has ice border accent and "(brain)" label in header
• Cannot be replaced by other terminals

4.2 Brain Terminal Auto-Open

• When fleet becomes active (honryu session detected), automatically:
  1. Create daemon terminal tab for brain session
  2. Pin to slot 0 in the active workspace
• When fleet deactivates, unpin slot 0

Files

• crates/kild-ui/src/views/main_view/pane_grid.rs — pinned slot concept
• crates/kild-ui/src/views/main_view/main_view_def.rs — auto-open brain terminal

Depends on

• Fleet UI Phase 1: Agent status visibility #563 (Phase 1: FleetStore + is_fleet_active detection)