Let a node composing itself hand a module exactly when the vault judged its plan handed, through one rule (catalogue.AssignmentHands), so the vault and the node never judge postgres's secrets two ways again (issue 774)

go/buscompose/accounts.go

@@ -187,12 +187,17 @@ func HeldCredential(w WantedAccount, password string) ([]byte, error) {
 		Claims: w.Claims})
 }
 
-// **One issuer at every moment: minting turns on at the lease write** (novox/hq ADR 0561 §3, §6). The controller's lease
-// is the one key `holder` of its bucket (LeaseBucket). The operator's credential hands it away by writing a value that
-// names its new holder in `handed-to`; while the key holds that, the vault mints and the grants part creates the durable
-// consumers an account needs. A controller's value, a key deleted or expired, or one that cannot be read or parsed, turn
-// both off: when in doubt nothing is minted, so the controller and the vault never both mint one account. No clock and
-// no setting turns it.
+// **The lease write** (novox/hq ADR 0561 §3, §6). The controller's lease is the one key `holder` of its bucket
+// (LeaseBucket). The operator's credential hands it away by writing a value that names its new holder in `handed-to`;
+// while the key holds that, the grants part creates the durable consumers an account needs, the assigner reads the grants
+// part's grants (delivery.GrantSource), and the vault retires and rotates accounts. A controller's value, a key deleted or
+// expired, or one that cannot be read or parsed, turn those off. No clock and no setting turns it.
+//
+// **Minting is no longer on the lease** (issue 774, research 072's gap "vault mints after the lease"): the vault is the
+// one issuer of every account the grants part wants, whoever holds the lease, and the controller mints none once a vault
+// is installed (it forwards `module issue` to the vault's issue-account). One issuer at every moment holds by who mints,
+// not by the lease: an account whose value the vault holds is never minted anew, and a value the controller hands or
+// moves never replaces one the vault minted.
 
 // ControllerLease is the lease's bucket as a reader names it; the vault and the grants part alone read it
 // (NamedReaders), the controller's announcement marking it readable by nobody.