Fix loop completion deadlock and queued prompt controls

[Obed0101]

Summary

• return terminal run_once results without waiting on an owner-session notification that would re-enter the same turn
• persist background loop notifications asynchronously and avoid duplicate direct-owner notifications
• keep Send now bound to the first visible queued user prompt when synthetic runtime messages are present
• extend native PTY coverage for queued prompts, transcript paging, and double-Esc cancellation

Validation

• bun run --cwd packages/opencode typecheck
• bun test --cwd packages/opencode test/session/loop.test.ts test/tool/loop.test.ts test/cli/tui/session-layout.test.ts (166 passed)
• git diff --check

Target branch: dev. Release packaging remains gated on the verified candidate SHA and the beta prerelease workflow.