Refuse the agent-home gap reached through a module's own directory or a literal home

A path written as ${dir:<id>} can resolve under the agent's home, and a
literal /home path may be it; both escaped the check (hq ADR 0266).

checks/agenthome/main.go

@@ -6,7 +6,9 @@
 // opened itself and refuses a link it finds; it unpacks an archive, and writes into an existing file (`into`:
 // json or block), only after checking the path, so a link swapped in between the check and the write would
 // point root's write at any file. No module does either today. This check keeps it so: a resource of type
-// `archive`, or a `file` with `into`, whose path is under ${machine:agent-home}, is refused.
+// `archive`, or a `file` with `into`, whose path is under ${machine:agent-home} — written so, reached through
+// one of the module's own directories (${dir:<id>}), or written as a literal /home path — is refused. The
+// node-engine refuses the same below the home of any account declared never to become root, whatever the path.
 //
 //	go run . <catalogue root>
 //
@@ -18,6 +20,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"sort"
 	"strings"
 )
@@ -25,6 +28,29 @@ import (
 // AgentHome is the machine fact naming the agent account's home.
 const AgentHome = "${machine:agent-home}"
 
+// ofDir is where a manifest names one of its own directories: ${dir:<id>}.
+var ofDir = regexp.MustCompile(`\$\{dir:([a-z0-9][a-z0-9_-]*)\}`)
+
+// resolve replaces each ${dir:<id>} with that resource's own path, as far as the manifest says it, so a path
+// reaching the agent's home through one of the module's directories is seen for what it is.
+func resolve(p string, dirs map[string]string) string {
+	for i := 0; i < 8 && ofDir.MatchString(p); i++ {
+		p = ofDir.ReplaceAllStringFunc(p, func(word string) string {
+			if to, ok := dirs[ofDir.FindStringSubmatch(word)[1]]; ok {
+				return to
+			}
+			return word
+		})
+	}
+	return p
+}
+
+// underAHome says whether a resolved path lies under the agent's home: by its machine fact, or written as a
+// literal home, which no definition may carry anyway (ADR 0112) and which may well be the agent's.
+func underAHome(p string) bool {
+	return strings.HasPrefix(p, AgentHome) || strings.HasPrefix(p, "/home/") || p == "/home"
+}
+
 // Finding is one resource refused.
 type Finding struct {
 	Module, ID, Why string
@@ -50,9 +76,16 @@ func Check(root string) ([]Finding, error) {
 		if err := json.Unmarshal(raw, &m); err != nil {
 			return nil, fmt.Errorf("%s: %w", path, err)
 		}
+		dirs := map[string]string{}
+		for _, r := range m.Resources {
+			id, _ := r["id"].(string)
+			if p, _ := r["path"].(string); id != "" && p != "" {
+				dirs[id] = p
+			}
+		}
 		for _, r := range m.Resources {
 			p, _ := r["path"].(string)
-			if !strings.HasPrefix(p, AgentHome) {
+			if !underAHome(resolve(p, dirs)) {
 				continue
 			}
 			id, _ := r["id"].(string)

checks/agenthome/main_test.go

@@ -25,11 +25,15 @@ func TestAnArchiveOrAFileWrittenIntoUnderTheAgentsHomeIsRefused(t *testing.T) {
 	manifest(t, root, "c", `{"id":"dir","type":"directory","path":"${machine:agent-home}/.claude"},`+
 		`{"id":"whole","type":"file","path":"${machine:agent-home}/x","content":"y"},`+
 		`{"id":"op","type":"archive","path":"${machine:account-home}/.local/share/x"}`)
+	manifest(t, root, "d", `{"id":"home","type":"directory","path":"${machine:agent-home}/.claude"},`+
+		`{"id":"inner","type":"directory","path":"${dir:home}/inner"},`+
+		`{"id":"via-dir","type":"archive","path":"${dir:inner}/theme"}`)
+	manifest(t, root, "e", `{"id":"literal","type":"file","path":"/home/agent/.bashrc","into":"block","content":"x"}`)
 	found, err := Check(root)
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(found) != 2 || found[0].Module != "a" || found[1].Module != "b" {
+	if len(found) != 4 || found[0].Module != "a" || found[1].Module != "b" || found[2].ID != "via-dir" || found[3].ID != "literal" {
 		t.Fatalf("refused %+v", found)
 	}
 }