CHW-4912 HardenAlreadyEmitted

harden bundle already emitted from this proposal; propose a new one to ship again

Default message: harden bundle already emitted from this proposal; propose a new one to ship again
HTTP status: 409 (client)

Problem. Emission was requested on a proposal that already shipped its bundle. Cause. The state transition is one-way: once a bundle has been rendered, the same proposal cannot ship again — otherwise the MANIFEST.toml audit trail would lose its “single emission” property. Fix. Propose a fresh bundle from the wizard (POST /api/hardening/approval/request); the new proposal id replaces the spent one. HTTP 409.