dep-scan.sh: capture govulncheck's real exit code and feed the reachability gate only on exit 0 (clean) or 3 (vulns found). Any other exit (crash, timeout, 137) is now INFRA, so a truncated-but-parseable JSON stream can no longer parse clean and yield a falsely attested posture. npm ci / npm audit / cargo audit stderr is captured and surfaced on failure (no more 2>/dev/null).
Dockerfile: the posture-builder stage no longer curl|sh's rustup.rs. The Rust toolchain is COPY --from=rust:1-bookworm (canonical official image, same base as desktop-builder) with RUSTUP_HOME/CARGO_HOME set -- stronger provenance than TLS-TOFU rustup, no pipe-to-shell inside the stage that produces the attestation. docker compose build will validate the new layer.
linux.sh.tmpl: guard the posture check under set -e so an un-attested (exit 3) or blocked (exit 4) verdict degrades honestly instead of aborting the install before POSTURE_RC is captured.
ETHOS #1 (errors are history), #3 (assume failure). CI-002 + CI-003.
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