docs(m177): handoff — §2 is code-complete, green, and deliberately uncommitted

Records the standing instruction it was written under: build through §6 with
clippy only, then run the unit suites and fmt once at the end. The tree is
dirty by design and every path in it is wanted — the file list says which.

Also records the §2 design calls a reviewer will ask about (why the verb
answers serialized bytes, why `Leasing` became an associated type, why two new
failure labels exist), that the live daemon predates the lease verb, and that
M183_001 rides in this PR.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>