Add an experimental, off-by-default `execute` tool that runs LLM-authored
JavaScript with a `tools.<name>(args)` proxy over connected MCP tools. When
OPENCODE_EXPERIMENTAL_CODE_MODE is enabled and MCP tools are present, the
session exposes the single code-mode tool instead of registering each MCP
tool directly; child calls route through the native permission path.
Code mode is defined via the standard Tool.define/Tool.init machinery so it
inherits arg decoding and output truncation from the shared wrapper. Tool
results are reduced to structured content or text, and the program's return
value is coerced to text without failing on shape.
Note: execution currently uses an in-process AsyncFunction with no isolation
or timeout; sandboxing is tracked as follow-up work.
Aiden Cline
49f20b6a30