Rename off the jsmnmq placeholder

[phall1]

The README says it plainly: "Name is a placeholder. jsmnmq is the repo dir. Rename before anyone outside sees it."

Bar D means strangers type it. It also blocks three pieces of opam metadata that opam lint currently warns about, because they need a real repository URL:

• homepage (opam lint warning 35)
• bug-reports (warning 36)
• (source (github <owner>/<repo>)) in dune-project

Exit criteria

• Name chosen
• Repo renamed and remote created
• dune-project metadata completed; opam lint clean
• README placeholder note removed

Do this before W5, not after — the published artifact carries the name.
See docs/END-STATE.md §7 risk 4, docs/TOOLCHAIN.md Known gaps.

[linear-code]

PHA-307