D5: an app restore works from the drive alone (v0.188.0)

The recovery unit on the customer's drive now carries the PORTABLE secret
class, so Tier-1/Tier-2 restore no longer depends on the whole-guest tier.
A customer needs the drive and nothing else.

Part 0's rulings overturned the brief's recommendation, on evidence:
- the data_key flag is untrustworthy (4+ encryption keys the catalog itself
  labels as such are unflagged) -> R-127
- a DB password is not resettable in practice: POSTGRES_PASSWORD is ignored
  once PGDATA is non-empty, so a regenerated value leaves the app unable to
  authenticate against its own restored rows while the dump replay still
  reports success (proven on a throwaway postgres:16-alpine)

Ruling (operator): type:secret travels, type:password never does, minus the
nonPortableSecrets code register. Plaintext -- withholding the internet-
reachable class is what licenses that, and the two are coupled.

Precedence: the UNIT WINS over the guest -- the unit's secrets were captured
in the same run as the dumps beside them, so they match the data being
restored. The fail-closed data-key gate is unchanged.

Secret values are never logged; the manifest records NAMES only.

REUSE.md

@@ -111,7 +111,9 @@
 | `SaveAppConfig` / `LoadAppConfigDecrypted` | controller/internal/stacks/deploy.go | `(stackDir, cfg, encKey, sensitiveVars)` | app.yaml persistence | Encrypts only `SensitiveEnvVars(meta)`; never write app.yaml directly |
 | `generateValue` / `randomAlphanumeric` | controller/internal/stacks/deploy.go | `(spec "password:N\|hex:N\|base64key:N\|static:v")` | Auto-generated secrets | crypto/rand-backed; reuse the spec grammar |
 | `Manager.GenerateSecretForField` | controller/internal/stacks/deploy.go | `(stackName, envVar) (string, bool)` | Replacement value for a RESETTABLE secret from its catalog `generate` spec (O4 restore path via `backup.SetSecretGenerator`) | REFUSES `data_key` fields, spec-less and non-secret fields; never log the value |
-| `reconcileRestoreSecrets` | controller/internal/backup/restore_unit.go | `(nonSecretEnv, recoveredSecrets, secretNames, dataKeyNames)` | Recovery-unit restore env merge | Units are secret-FREE by design; secrets come from live app.yaml |
+| `reconcileRestoreSecrets` | controller/internal/backup/restore_unit.go | `(nonSecretEnv, unitSecrets, guestSecrets, secretNames, dataKeyNames)` | Recovery-unit restore env merge | **Precedence: UNIT WINS over guest** (the unit's secrets match the data being restored; the guest's are merely newest). Pure — new sources arrive as ARGUMENTS. Fail-closed data-key gate lives here |
+| `stacks.PortableSecretEnvVars` | controller/internal/stacks/deploy.go | `(meta) []string` | **THE D5 secret boundary**: which secrets may travel on a customer drive | `type: secret` travels, `type: password` NEVER, minus the `nonPortableSecrets` code register. Withholding the password class is what licenses plaintext — do not relax one without the other |
+| `buildUnitAppYaml` / `readUnitEnv` | controller/internal/backup/{recovery_unit,restore_unit}.go | `(info) []byte` / `(path, portableNames)` | The ONE place the unit's app.yaml is written / split back | Split is driven by the MANIFEST's portable names, never guessed from key names; write 0600; empty `portableNames` = schema-1 unit ⇒ everything is plain config |
 | `EncryptFile` / `DecryptFile` / `IsEncryptedFAB` | controller/internal/appexport/crypto.go | password-based file crypto | .fab export bundles | scrypt-derived AES+HMAC keys |
 | `maskRepoURL` | controller/internal/sync/sync.go | `(url) string` | Logging git URLs | Strips embedded credentials |
 | `metrics.RedactLine` | controller/internal/metrics/redact.go | `(s string) string` | ANY log line shipped off-box (issue context, log tails) | Masks password/passwd/secret/token/api-key/authorization/bearer values + 64-hex; apply BEFORE the line leaves the box — controller-side redaction is authoritative |