Expose connected MCP tools to code mode as per-server namespaces
(`tools.<server>.<tool>(args)`) and generate the execute tool description
from the catalog: one namespace block per server, each tool rendered with a
TypeScript-style input signature derived from its JSON schema plus its
description, and the calling convention stated up front.
The server/tool split is cosmetic; child-call routing re-joins the segments
into the existing flat catalog key, so it stays exact regardless of
underscores in server or tool names.
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