refactor(permissions): drop the unused permission-issuer lookup

listUserPermissionIssuers and its store method listUserPermissionIssuerIds
existed to synthesize the filesystem root from the home directories of everyone
who had granted the caller a permission. That listing is gone — it advertised
folders readdir then refused to open — and the share index answers "who shared
with me" directly, so nothing wants them back.

One removed test only asserted that the call returned an array; the other
covered readLinkedUserUserPerms round-tripping and is kept, rewritten without
the issuer lookup.

src/backend/services/permission/PermissionService.test.ts

@@ -621,37 +621,8 @@ describe('PermissionService (integration)', () => {
         });
     });
 
-    describe('listUserPermissionIssuers / queryIssuerHolderPermissionsByPrefix', () => {
-        it('listUserPermissionIssuers returns the issuer who granted the target a perm', async () => {
-            const { user: issuer, actor: issuerActor } = await makeUserActor();
-            const { user: target } = await makeUserActor();
-            const permission = `zztest:lst-${uuidv4()}:ii:read`;
-            await server.stores.permission.setFlatUserPerm(
-                issuer.id,
-                `manage:${permission}`,
-                {
-                    permission: `manage:${permission}`,
-                    deleted: false,
-                    issuer_user_id: issuer.id,
-                } as never,
-            );
-            await runWithContext({ actor: issuerActor }, () =>
-                permService.grantUserUserPermission(
-                    issuerActor,
-                    target.username,
-                    permission,
-                ),
-            );
-            // listUserPermissionIssuers is best-effort; just verify it runs
-            // and either includes the issuer or returns an empty array (the
-            // linked store may not be populated immediately).
-            const issuers = await permService.listUserPermissionIssuers({
-                id: target.id,
-            });
-            expect(Array.isArray(issuers)).toBe(true);
-        });
-
-        it('queryIssuerHolderPermissionsByPrefix returns [] for actors without user.id', async () => {
+    describe('queryIssuerHolderPermissionsByPrefix', () => {
+        it('returns [] for actors without user.id', async () => {
             const out = await permService.queryIssuerHolderPermissionsByPrefix(
                 { user: undefined } as unknown as Actor,
                 { user: undefined } as unknown as Actor,

src/backend/services/permission/PermissionService.ts

@@ -1343,26 +1343,6 @@ export class PermissionService extends PuterService {
 
     // -- Issuer queries (share discovery et al) -----------------------
 
-    async listUserPermissionIssuers(user: {
-        id: number;
-    }): Promise<Array<UserRowSummary | null>> {
-        const ids = await this.stores.permission.listUserPermissionIssuerIds(
-            user.id,
-        );
-        const usersById = await this.stores.user.getByIds(ids);
-        return ids.map((id) => {
-            const u = usersById.get(id);
-            return u
-                ? {
-                      id: u.id,
-                      uuid: u.uuid,
-                      username: u.username,
-                      email: u.email,
-                  }
-                : null;
-        });
-    }
-
     async queryIssuerPermissionsByPrefix(
         issuer: { id: number },
         prefix: string,

src/backend/stores/permission/PermissionStore.test.ts

@@ -828,7 +828,7 @@ describe('PermissionStore', () => {
     // -- user → user ------------------------------------------------------
 
     describe('user-to-user permissions', () => {
-        it('lists issuers for a holder and clears them on revoke', async () => {
+        it('reads a holder grant back and clears it on revoke', async () => {
             const issuer = await makeUser();
             const holder = await makeUser();
             await store.upsertUserUserPerm(
@@ -838,10 +838,6 @@ describe('PermissionStore', () => {
                 {},
             );
 
-            expect(
-                await store.listUserPermissionIssuerIds(holder.id),
-            ).toContain(issuer.id);
-
             const rows = await store.readLinkedUserUserPerms(holder.id, [
                 'fs:u:read',
             ]);

src/backend/stores/permission/PermissionStore.ts

@@ -360,14 +360,6 @@ export class PermissionStore extends PuterStore {
         );
     }
 
-    async listUserPermissionIssuerIds(holderUserId: number): Promise<number[]> {
-        const rows = await this.clients.db.read(
-            'SELECT DISTINCT issuer_user_id FROM `user_to_user_permissions` WHERE `holder_user_id` = ?',
-            [holderUserId],
-        );
-        return rows.map((r) => Number(r.issuer_user_id));
-    }
-
     // -- SQL: user-to-app permissions --------------------------------
 
     async readUserAppPerms(