[bug] Terminal ghosting and accumulating black regions after workspace switches #3351

Describe the bug

When switching away from a workspace that contains a running terminal pane and then coming back, the terminal briefly renders the correct content and then falls into a corrupted visual state.

The key symptom is not just "blank output" or "slow repaint".
The content can appear correctly for a moment, then large black blank regions take over the view. Repeating the workspace switch makes the problem worse: each switch appears to add another ghost/stale terminal layer or another large blank region.

This makes the terminal effectively unreadable.

Expected behavior

Returning to an existing terminal pane after a workspace switch should preserve the visible terminal state exactly, or at minimum repaint into a clean usable state without accumulating artifacts.

Actual behavior

After switching away from a workspace and returning to the same terminal pane:

• the terminal may flash the correct content briefly
• then large black blank regions appear over the terminal
• repeated workspace switches make the corruption worse
• the terminal becomes unreadable because ghost/stale terminal regions accumulate

This does not look like missing PTY output. It looks like a post-attach / post-visibility renderer or restore lifecycle bug.

Reproduction

1. Open a workspace with a terminal pane.
2. Start a dense TUI workload inside the terminal (for example Codex CLI).
3. Switch to another workspace.
4. Return to the original workspace.
5. Observe a brief correct render followed by black blank regions / stale terminal ghosting.
6. Repeat workspace switching a few times.
7. Observe that the corruption accumulates and readability gets worse on each switch.

Observed pattern

The strongest signal is this:

• the correct content is visible for a moment
• then a later lifecycle pass corrupts the pane

That suggests the failure is after terminal output arrives.
So this appears to be a render / restore / reattach problem, not a subprocess output problem.

Environment

• Superset Desktop: 1.4.7
• macOS: Apple Silicon
• workload inside terminal: Codex CLI

Related issues

This looks related to the same family, but more severe / more cumulative:

• [bug] when focusing back on terminal, content gets corrupted #3208
• [bug] Codex terminal state corrupts on pane reattach after tab/workspace switch #3309
• [bug] Terminal can still repaint into a stale visual state after focus/workspace restore #3321

The specific difference here is the progressive ghosting / accumulating black regions after repeated workspace switches.

Additional notes

I intentionally omitted private/local environment details and internal workspace names. If a maintainer wants a smaller public repro or wants me to test a candidate patch, I can do that.