The QuadletUnit struct now covers everything a backend manifest needs
(ports, environment, devices, add_hosts, entrypoint+command, read-only
root, no_new_privileges, cpu_quota, restart policy choice). Adds
QuadletUnit::from_manifest(&AppManifest, name) that translates a parsed
manifest into a unit, plus parse_memory_mib for "1g"/"512m"/raw-MiB
forms. The renderer skips empty/false directives so existing companion
units render byte-identically — no behavior change for shipping
companions; the backend renderer is dead code until Phase 3.2 wires it
into the orchestrator.
Eight new unit tests cover:
* parse_memory_mib forms (1024, 512m, 2g, garbage)
* shell_join quoting (whitespace, embedded quotes)
* RestartPolicy → systemd string mapping
* render emits backend directives when set
* render skips them when defaulted (companion regression gate)
* from_manifest happy path on a bitcoin-knots-shaped manifest
* from_manifest read-only volume detection
* from_manifest tmpfs filtering
* end-to-end manifest → render bytes assertion
Tests: 615 → 624 (+9 net; one pre-existing parse_memory_mib path was
implicitly covered before but is now explicit). Cargo warnings: 0.
`from_manifest`, `parse_memory_mib`, and `RestartPolicy::OnFailure` are
marked allow(dead_code) with explicit references to Phase 3.2 — if
3.2 doesn't wire them, the dead-code warning resurfaces.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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