The mesh owns the operator's ~/.ssh: account fact + home-scoped resources (to-be 29)

A node carries its operator account (name + home; migration 0036, Node.Account,
SetAccount, 'node account' CLI). The account and its home are offered as
machine facts ${machine:account} / ${machine:account-home}, and machineInto
now resolves placeholders in a resource's path and owner (not just content), so
a module writes into a person's home naming what it cannot know. A RosterFile
gains Home: the file is placed under the account's home and chowned to it, its
template sees each node's Account, and a machine with no account gets none —
this is how the ssh Host blocks for every node reach a person's ~/.ssh. Roster
carries per-node accounts (Rendering.Accounts). Tested, including ssh-client
composed end-to-end. Not deployed.

internal/catalogue/declaration.go

@@ -103,6 +103,11 @@ type Rendering struct {
 	// and offered as ${machine:mesh-range}, the same way one machine's address is.
 	MeshRange string
 
+	// Accounts is each machine's operator account, by the same internal name Names uses (novox/hq
+	// to-be 29). What an ssh Host block's `User` line is composed from; empty for a machine no
+	// operator account is known on.
+	Accounts map[string]string
+
 	// Kept is every operator-sealed secret in the mesh, for a module that `keeps` them. Nil when
 	// nothing on this node keeps them, or the mesh has no operator key.
 	Kept *KeptExport
@@ -656,7 +661,7 @@ func (r Resolution) compose(with Rendering, owner map[string]string) ([]map[stri
 		// plane's; making a name resolve is the module's software. Emitted as ordinary files under
 		// this module's name, so they are applied, reported and removed exactly as anything else
 		// it declares.
-		given, err := FactsInto(m, r, with.Names, with.Machines, with.Suffix)
+		given, err := FactsInto(m, r, with.Names, with.Machines, with.Accounts, with.Suffix)
 		if err != nil {
 			return nil, err
 		}