fix(notify): cross-platform TTY write — /dev/tty unavailable in OpenCode plugin context on Windows

[MoerAI]

Bug Description

warpNotify() in notify.ts writes OSC 777 escape sequences via writeFileSync("/dev/tty", ...). This fails silently on Windows because /dev/tty is a Unix-only device. The catch block swallows the error, so no notifications ever reach Warp on Windows (and possibly other platforms where the plugin subprocess lacks a controlling terminal).

This causes:

• Setup chip never disappears (Warp never receives session_start)
• No notifications for task completion, permission requests, or tool use
• Plugin appears non-functional despite being correctly installed

Root Cause

OpenCode plugins run as JavaScript modules inside a Bun/Node.js subprocess managed by OpenCode's plugin loader. Unlike Claude Code's shell-based hooks (which execute printf ... > /dev/tty in bash with direct terminal access), the OpenCode plugin's writeFileSync("/dev/tty") fails because:

1. Windows: /dev/tty doesn't exist in the Windows filesystem — Node.js uses native Win32 file APIs
2. Plugin subprocess: Even on Unix, the plugin process may not have /dev/tty accessible if OpenCode spawns it with redirected stdio

Why PR #12's process.stdout.write() fallback doesn't work

PR #12 falls back to process.stdout.write(sequence) on failure. Users confirmed this still doesn't work because process.stdout in the plugin subprocess is piped to OpenCode's plugin loader for RPC communication — it doesn't reach the terminal.

Proposed Fix

Replace the single /dev/tty write with a platform-aware cascade:

1. Unix: Try writeFileSync("/dev/tty") (existing behavior, works when controlling terminal is available)
2. Windows: Try writeFileSync("CONOUT$") then writeFileSync("CON") — Windows console output devices that bypass stdio redirection
3. Fallback: Try process.stderr.write() (stderr is less commonly redirected than stdout)

Additionally, port the WARP_CLIENT_VERSION validation from claude-code-warp's should-use-structured.sh to avoid sending notifications to known-broken Warp builds that set WARP_CLI_AGENT_PROTOCOL_VERSION but can't render structured notifications.

Environment

• Affected OS: Windows 11 (confirmed), possibly macOS
• Warp: Latest stable
• OpenCode: 1.4.5+
• Plugin version: 0.1.5

Related

• Issue Plugin setup notification never disappears (plugin not recognized as installed) #11 — user reports with reproduction steps
• PR Fix: notifications broken on Windows (writeFileSync /dev/tty) #12 — partial fix attempt (stdout fallback)
• warpdotdev/claude-code-warp should-use-structured.sh — version gating reference