web: clipboard paste doesn't work in prompt input on iOS

Summary

Clipboard paste does not work in the opencode web app on iOS devices. Long-press / paste into the prompt input has no effect.

Environment

• opencode version: 2.0.3 (server)
• OS: Linux omarchy 7.2.3-arch1-3 #1 SMP PREEMPT_DYNAMIC Sun, 06 Sep 2026 13:01:04 +0000 x86_64 GNU/Linux (server host)
• Terminal: Unavailable: web UI issue, not terminal
• Shell: Unavailable: web UI issue
• Install/channel: latest
• Active plugins: local plugins found (fileview.ts, loop-manager.ts in ~/.config/opencode/plugins/), no registry plugin entries in opencode.json
• Client: iOS (version Unavailable — reporter to confirm), browser Unavailable (likely Mobile Safari / PWA, reporter to confirm), accessing self-hosted web UI remotely

Reproduction

1. Open the opencode web app on an iOS device.
2. Focus the prompt / chat input.
3. Copy text elsewhere on iOS, then long-press -> Paste (or use clipboard / keyboard paste).
4. Observe input.

Expected Behavior

Pasted text should appear in the prompt input, same as desktop web.

Actual Behavior

Paste has no effect — clipboard contents do not appear in the input. Seems like clipboard paste doesn't work at all on iOS.

Additional Context

• Frequency: consistently reproducible per reporter (needs iOS version confirmation).
• No related iOS paste issue found — existing paste issues cover Windows Terminal, TUI bracketed paste, VS Code terminal, image paste, but none for iOS web UI. Existing iOS issues cover PWA safe-area overlap (#35480), stop button obscured (#38210), narrow viewport layout (#48739, #48260, #43295, #37545).
• Workarounds tried: none known.
• Suspect areas: mobile web prompt input handling, preventDefault on paste/touch events, missing paste event listener or clipboard-read permission flow on iOS Safari, virtual keyboard / contenteditable handling.