Retain tunnel annotations through address declaration, then hand only
the bindable overlay to exact-type transport lookup and dialing.
Broaden `Channel.from_addr()` and `_connect_chan()` inputs accordingly,
and cover plain plus tunnelled TCP dispatch arguments.
Prompt-IO: ai/prompt-io/opencode/20260819T213144Z_f81fc5e5_prompt_io.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
