v0.9.0

v0.9.0 — il token che si incolla: il tool quota, non il lettore

The delivery model of 0.8.0 is untouched. This release closes the token surface:
an agent-name grammar (one shell word, reversible derivation from a directory),
every printed path and address rendered as one shell argument by the tool
(internal/shellarg: peers SCOPE column, next fromAddressShellArg, every
remediation), register --resume by identity, lock errors that state facts and no
remedy, the README rewritten around the binary and validated black-box, Makefile
and CI as strict as the local gate, CLAUDE.md out of the repository.

Gate on main at this commit: go test -race -count=1 -> 12/12, 0 FAIL, 0 cached.