Standalone binary: built-in tools fail with 'Bun is not defined' on Linux x86_64

Description

The opencode v1.18.5 standalone Linux binary (opencode-linux-x86_64.tar.gz) has a runtime bug where the built-in file system tools (Read, Write, Edit, Glob, Grep) fail with Bun is not defined:

Bun is not defined

The binary is a Bun-compiled ELF (bun build --compile), so the Bun global should be available. It is not, causing any tool that uses Bun.file(), Bun.write(), or similar Bun-specific APIs to fail.

Impact

• Read tool: cannot read files
• Write tool: cannot write files
• Edit tool: cannot edit files
• Glob tool: cannot search files
• Grep tool: cannot search content
• Bash tool: works fine (does not use Bun file APIs)

This makes the binary nearly unusable for coding tasks that require file operations.

Reproduction

1. Download and extract opencode-linux-x86_64.tar.gz from v1.18.5 release
2. Run opencode in TUI mode
3. Try any file operation (Read, Write, Edit)
4. Observe: Bun is not defined

Environment

• Binary: opencode-linux-x86_64 v1.18.5
• OS: Linux (tested on Ubuntu 24.04)
• Arch: x86_64
• Bun v1.3.14 installed on system (does not help — the standalone binary should bundle its own runtime)

Additional context

• Installing bun on the system PATH does not resolve the issue — the error is in the compiled binary's internal runtime
• Upgrading @opencode-ai/plugin (node_modules) from 1.17.8 to 1.18.5 does not help
• The opencode web subcommand works (starts the web server successfully), as does CLI mode for non-tool operations
• Not related to #39017 (web UI content-type) or #38789 (desktop app) — different manifestation of what may be the same underlying standalone compilation issue

Reproduce the failure with the v1.18.5 opencode-linux-x86_64 standalone binary on Ubuntu 24.04, then inspect the bun build --compile packaging and runtime path for the built-in file tools. Done means Read, Write, Edit, Glob, and Grep work without “Bun is not defined” while Bash and web behavior remain intact.