Abort leaves orphaned task calls pending

Description

If OpenCode loses the in-memory runner for a session while a task tool call is still persisted as pending or running, aborting the session only marks it idle. The parent assistant message and task part remain unfinished, so the transcript shows a task that never completed.

The TUI startup path for --continue --fork can also briefly route through a placeholder session ID (dummy), which produces an invalid-session error instead of returning to home when no session is available.

Steps to reproduce

1. Start a session that invokes the task tool.
2. Interrupt or restart the local runner after the task part is persisted but before it reaches a terminal state.
3. Abort the parent session.
4. Observe the task part still shown as pending or running and its assistant message left incomplete.

For the fork path:

1. Run opencode --continue --fork with no resumable root session.
2. Observe the placeholder-session validation error.

Expected behavior

Abort should cancel any live runner, then settle orphaned task parts with an aborted error and complete their parent assistant message. --continue --fork should show a loading state and return home with an error when no session can be forked.

Plugins

None

OpenCode version

1.18.x

Operating System

Linux

Terminal

Terminal emulator