refactor: harden plugin install flow and main DM route pinning

src/security/dm-policy-shared.test.ts

@@ -7,6 +7,7 @@ import {
   resolveDmGroupAccessDecision,
   resolveDmGroupAccessWithLists,
   resolveEffectiveAllowFromLists,
+  resolvePinnedMainDmOwnerFromAllowlist,
 } from "./dm-policy-shared.js";
 
 describe("security/dm-policy-shared", () => {
@@ -106,6 +107,43 @@ describe("security/dm-policy-shared", () => {
     expect(lists.effectiveGroupAllowFrom).toEqual([]);
   });
 
+  it("infers pinned main DM owner from a single configured allowlist entry", () => {
+    const pinnedOwner = resolvePinnedMainDmOwnerFromAllowlist({
+      dmScope: "main",
+      allowFrom: [" line:user:U123 "],
+      normalizeEntry: (entry) =>
+        entry
+          .trim()
+          .toLowerCase()
+          .replace(/^line:(?:user:)?/, ""),
+    });
+    expect(pinnedOwner).toBe("u123");
+  });
+
+  it("does not infer pinned owner for wildcard/multi-owner/non-main scope", () => {
+    expect(
+      resolvePinnedMainDmOwnerFromAllowlist({
+        dmScope: "main",
+        allowFrom: ["*"],
+        normalizeEntry: (entry) => entry.trim(),
+      }),
+    ).toBeNull();
+    expect(
+      resolvePinnedMainDmOwnerFromAllowlist({
+        dmScope: "main",
+        allowFrom: ["u123", "u456"],
+        normalizeEntry: (entry) => entry.trim(),
+      }),
+    ).toBeNull();
+    expect(
+      resolvePinnedMainDmOwnerFromAllowlist({
+        dmScope: "per-channel-peer",
+        allowFrom: ["u123"],
+        normalizeEntry: (entry) => entry.trim(),
+      }),
+    ).toBeNull();
+  });
+
   it("excludes storeAllowFrom when dmPolicy is allowlist", () => {
     const lists = resolveEffectiveAllowFromLists({
       allowFrom: ["+1111"],

src/security/dm-policy-shared.ts

@@ -4,6 +4,28 @@ import type { ChannelId } from "../channels/plugins/types.js";
 import { readChannelAllowFromStore } from "../pairing/pairing-store.js";
 import { normalizeStringEntries } from "../shared/string-normalization.js";
 
+export function resolvePinnedMainDmOwnerFromAllowlist(params: {
+  dmScope?: string | null;
+  allowFrom?: Array<string | number> | null;
+  normalizeEntry: (entry: string) => string | undefined;
+}): string | null {
+  if ((params.dmScope ?? "main") !== "main") {
+    return null;
+  }
+  const rawAllowFrom = Array.isArray(params.allowFrom) ? params.allowFrom : [];
+  if (rawAllowFrom.some((entry) => String(entry).trim() === "*")) {
+    return null;
+  }
+  const normalizedOwners = Array.from(
+    new Set(
+      rawAllowFrom
+        .map((entry) => params.normalizeEntry(String(entry)))
+        .filter((entry): entry is string => Boolean(entry)),
+    ),
+  );
+  return normalizedOwners.length === 1 ? normalizedOwners[0] : null;
+}
+
 export function resolveEffectiveAllowFromLists(params: {
   allowFrom?: Array<string | number> | null;
   groupAllowFrom?: Array<string | number> | null;