A login moves its node; an API key is added from any node, sealed (novox/hq ADR 0209)

The manager binds the node a login was adopted from to that login's licence,
switching it if it was bound to another; serves public_key; adopt takes a
key sealed to it. claude-code gains claude_code_add_api_key: read a file on
this node, seal, hand to adopt, remove the file, optionally switch here.

modules/claude-code/cmd/claude-code/node.go

@@ -343,6 +343,54 @@ func Apply(p Paths, c Current, write WriteManaged) (map[string]any, error) {
 	return out, nil
 }
 
+// AddAPIKey adds an API key from a file on this node to the licence manager (ADR 0209): sealed to the
+// manager's public key, handed to the seat's `adopt` on request/reply, and the file removed once taken. With
+// useHere, this node is switched to the new licence. The key never crosses the bus in the clear and is
+// never an argument.
+func AddAPIKey(p Paths, name, file string, useHere bool, ask Ask) (map[string]any, error) {
+	raw, err := os.ReadFile(file)
+	if err != nil {
+		return nil, fmt.Errorf("the key is read from a file on this node: %w", err)
+	}
+	key := strings.TrimSpace(string(raw))
+	if key == "" {
+		return nil, fmt.Errorf("%s is empty", file)
+	}
+	answer, err := ask(SeatVerb("public_key"), map[string]any{})
+	if err != nil {
+		return nil, err
+	}
+	var pk struct {
+		PublicKey string `json:"public_key"`
+	}
+	if err := json.Unmarshal(answer, &pk); err != nil || !strings.Contains(pk.PublicKey, "PUBLIC KEY") {
+		return nil, errors.New("the licence manager did not say what key to seal to")
+	}
+	box, err := Seal(key, pk.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+	adopted, err := ask(SeatVerb("adopt"), map[string]any{"name": name, "sealed": box, "from": p.Node})
+	if err != nil {
+		return nil, err
+	}
+	out := map[string]any{"adopted": json.RawMessage(adopted)}
+	// Taken: the key now lives encrypted in the manager's store alone.
+	if err := os.Remove(file); err != nil {
+		out["file"] = "could not be removed: " + err.Error()
+	} else {
+		out["file"] = "removed"
+	}
+	if useHere {
+		switched, err := ask(SeatVerb("switch"), map[string]any{"consumer": p.Node, "licence": name})
+		if err != nil {
+			return out, fmt.Errorf("adopted, and switching this node to it failed: %w", err)
+		}
+		out["switched"] = json.RawMessage(switched)
+	}
+	return out, nil
+}
+
 // ---- MCP servers ----------------------------------------------------------------------------------
 
 // Registration is a server registered (or, with no entry, unregistered) through this module.