fix(workspace): reconcile exited sessions to close stale pane/workspace

[Copilot]

Summary

Handle PTY sessionClosed events in AppModel so exit no longer leaves a dead pane/workspace rendered with no live session.

• Root cause
  • TerminalEvent.sessionClosed was emitted but not consumed by workspace runtime state.
• Behavior change
  • Closed session in multi-pane workspace → remove only that pane.
  • Closed session as last pane → close that workspace runtime; if none remain, close terminal window.
• Implementation
  • Added SessionClosedAction decision path + reconciliation flow in AppModel.
  • Added focused app tests for action selection.

case .sessionClosed(let session):
  reconcileClosedSession(session)

Layer touched

• PTY / sessions
• VT bridge / terminal state
• Renderer (Metal / cell-grid / text)
• Smooth scroll / history browse
• Workspace / splits / panes
• Settings / themes / UI chrome
• AI CLI integration (notifications, side input)
• Docs / CI / scripts
• Tests only

User-visible behavior

Typing exit in a pane now tears down that exited session from workspace state instead of leaving the UI stuck on a dead terminal surface.
If that pane was the workspace’s last live session, the workspace closes; if it was the last workspace, the window closes.

How I tested

scripts/check-architecture.sh
swift build            # blocked in this environment: missing vendored ghostty/zig-out artifacts
swift test             # blocked in this environment: missing vendored ghostty/zig-out artifacts

swift build && swift test && scripts/check-architecture.sh
# UI / renderer changes: also
./scripts/build-app-bundle.sh release

Checklist

• swift test passes
• scripts/check-architecture.sh passes (Core does not import SwiftUI)
• Commit messages follow Conventional Commits
• Docs updated if applicable

• Fixes [Bug]: The workspace stuck after executing 'exit' #1

[freecodetiger]

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