UI-agnostic helpers for resolving an MCP login target.
The MCP login flow historically inlined config discovery, trust gating,
shape validation, and print()-based error reporting. The TUI cannot
consume those print statements, so this module extracts the same logic
into pure functions that return structured results (ConfigResolution,
ServerSelection) plus a typed ConfigResolutionError. Callers decide
how to render those results.
No print() calls live in this module. No imports happen at module
top level beyond dataclasses/typing/pathlib so the CLI fast path
stays cheap; the actual config loaders are imported inside the
functions that need them.
