bug(workspace): terminal view hides which related agent a pane is showing #858

Expected

When a grid pane shows a related agent (an orchestration child or linked agent picked from the pane header's related-agent chips), the pane makes clear which agent is displayed and lets you switch back, in both Agent view and Terminal view.

Actual

In Terminal view the related-agent chips are not rendered. Grid-related selections persist (gridRelatedSelections), and WorkspaceLeaf mounts the selected related session in the terminal branch (sessionId={renderedSessionId}, src/renderer/src/workspace/tile-tree/TileTree.tsx). So after picking child B in pane A's chips and switching the pane to Terminal view, the pane shows B's raw TUI under A's pane label, with nothing indicating it is B and no way back short of switching views.

Reproduce

1. In Agent view, open a pane with related agents and pick a child in the header chips.
2. Switch that pane (or the global agent view mode) to Terminal.
3. The pane now shows the child's raw terminal with the parent's label and no chips.

Why it isn't a one-line fix

Showing the chips in Terminal view adds a header row, and the header's height is taken out of the PTY. Chips appearing or disappearing (for example when a child spawns) would resize the live provider TUI. That tradeoff needs a decision: always reserve the row, show a compact indicator in the status row, or accept the resize.

Impact

Confusing identity: the user can type into the wrong agent's TUI believing it is the parent.

Environment

main at 48ea691. Found in review of #853, which moved Terminal view onto the shared PaneHeader.