v0.18.1

Every way into the CLI now reports failure honestly. Previously a mistyped command, a script that raised, and a refused operation could each finish with exit status 0 and print nothing, so a CI step could report success for work it never did.

Fixed: unknown subcommands exited 0 silently; direct-file execution (the shebang path) swallowed errors and exited 0; env/store/app/pkg printed a refusal and then performed the refused operation; bundle accepted a missing input without a diagnostic; unknown subcommands under channel/registry/project printed help and exited 0, with parse errors on stdout and a lone dash silently dropped.

Adds an exit-contract gate: 43 checks over every CLI entry point, each verified in both directions, running on release binaries rather than dev builds only.

Existing projects build without changes.