Add reviewed MCP host configuration examples

[reacher-z]

Context

The read-only MCP server works from its installed-style executable bin, but alpha users need safe host configuration examples for a source checkout.

Scope

Document two reviewed stdio host configurations: one using the built package bin and one using an explicit absolute path to the built stdio entrypoint.

Acceptance criteria

• Begin from clone, locked install, and build commands.
• Explain that stdout is reserved for JSON-RPC and the server exposes only validate, plan, and fixed-schema tools.
• Explain the local stdio trust boundary and external resource limits.
• Use placeholders instead of a real username or home directory.
• Validate JSON snippets and all local links.
• Do not add mutation, run, filesystem, shell, or network tools.