[FEATURE]: A delayed prompt send feature for pre-scheduling a prompt to send #35653

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Summary

Add a delayed prompt send feature that lets users queue a prompt to be sent later in the same active opencode chat/session while the opencode process is still running.

Example:
(in the prompt input)

/delay_send 3h <prompt_content>

Problem

When the 5-hour limit is reached in the middle of a session, I currently have to wait until the next usage window and manually come back to send a continuation prompt.

This is inconvenient when I already know what I want to ask next, and I want the agent to continue in the same session so the existing context is preserved.

Proposed Solution

Support a command like:

/delay_send 3h Continue from where we left off and finish the remaining implementation.

This would keep the prompt queued locally and send it 3 hours later in the same chat/session, assuming the opencode process is still running.

Desired Behavior

• Queue a prompt to be sent after a delay.
• Send the prompt in the same active chat/session.
• Preserve the current session context.
• Optionally allow users to list or cancel queued delayed prompts.

Why This Helps

This would reduce friction when usage limits interrupt an active coding session. Users could queue a continuation prompt ahead of time instead of needing to manually return at the next window start time.