CLI fails with unrecognized flag --port when launched from editor extension

Description

When launching OpenCode from editor extensions (such as sdks/vscode/src/extension.ts which invokes opencode --port <port>), the CLI exits with:

ERROR
  Unrecognized flag: --port in command opencode

Additionally, the legacy shims in install and packages/cli/script/publish-aur.ts use exec "$(dirname "$0")/opencode" "$@". When the shim is invoked through a symlink (e.g. from ~/.local/bin or /usr/local/bin), $(dirname "$0") points to the directory containing the symlink rather than the installed binary, resulting in:

exec: .../opencode: cannot execute: No such file or directory

Steps to reproduce

1. Run opencode --port 40879
2. Observe Unrecognized flag: --port in command opencode
3. Symlink opencode2 shim into ~/.local/bin/opencode2 and run opencode2
4. Observe cannot execute: No such file or directory

OpenCode version

v2.0.3

Operating System

macOS / Linux