Image preparation must retain protected trust advancement when the image or candidate output fails later. Add updates:prepare and prepareRuntimeFirmwareUpdate, keeping one writer lease over one journaled SDK metadata pass, release-floor commit, actual image authentication, candidate writes and readback. An image hash failure, output collision or interruption preserves accepted metadata and release floors.
The protected path and standalone signed stager share the candidate file writer. A prepared candidate uses the currently authenticated protected root and archives active role metadata, including cached roles. Independent inspection takes its root pin from independently pinned store readback. The portable receipt does not provide current authorization. Both consistent-snapshot filename modes are covered.
The new native Stacks command has inferred flags and is registered in the compiled CLI. Documentation and the issue9 coverage map now distinguish implemented host preparation from remaining coordinator work.
Validation: the focused 10-file gate passed 86 tests and 535 assertions; after adding a controlled post-write image-corruption regression, the nine preparation cases passed with 66 assertions, plus runtime types and Pickier. App types, docs/roadmap/parity, compilation, 11 copied preparation operations, eight prior copied metadata operations and four retained actual SIGKILL/competing-writer cuts passed. The prior metadata CLI also read and recovered the new preparation failure state before the new CLI successfully prepared again. Both independent review axes have no actionable findings. Full exact-head CI for ce65c903e9eb42dd584e12a542470ccd74096fff is pending qualification. This source is not on main.
This builds on #46 (0ee8f27522e55ddee3ae6315660dd847423e33d1), whose separate full CI remains in progress. The diff includes that prerequisite until it reaches main. Issue #42 remains open with all acceptance checkboxes unchecked: durable candidate ownership, installed/known-good slots, current-policy rollback, key revocation/repair, exact-image boot/session health and comprehensive storage-fault campaigns are unfinished. Metadata recovery never grants candidate authorization. Physical deployment is disabled; no flashing, arming or actuator authority is added. Refs #9 and #42.