jetson-derive-carrier

Customize first-run gate for any customize-* skill on a custom carrier. Resolve the active target per target-platform-contract.md. Refuse if no custom_carrier: block, or if <source.root_path>/Linux_for_Tegra/.git is missing (jetson-init-source first). Template file create/copy rows land in a single overlay-tracker commit and copy directly to the custom-carrier-renamed target path — reference-named pristine files are never staged (see Fork plan for the local rule, which overrides the standard pristine + customization split from the workflow); conf-chain discovery follows per-board conf dispatch. Kernel base DTB is not forked — carrier deltas layer as a DT overlay wired via OVERLAY_DTB_FILE.