refactor(settings): scope the settings project selector to settings

Picking a project in Settings called setActiveProject, which relocates
the chat, the session list, the file tree and the Git surface. Reading
another project's MCP servers or agents moved the user's whole app.

It had to, because the configuration stores resolved the directory
themselves from the active project and held one flat list. Each of them
now takes an explicit directory — omitted still means the active project,
so every caller outside Settings is unchanged — and keys loaded data by
directory next to a flat mirror of the active project. Chat, autocompletes
and pickers keep reading that mirror; a load for another directory writes
only the map. A failed load restores that directory's previous list.

Settings resolves its own directory through useSettingsDirectory, backed
by a session-local settingsProjectPath that follows the active project
until the user picks something else.

packages/ui/src/components/sections/shared/SettingsProjectSelector.tsx

@@ -8,6 +8,8 @@ import {
 } from '@/components/ui/dropdown-menu';
 import { Icon } from "@/components/icon/Icon";
 import { useProjectsStore } from '@/stores/useProjectsStore';
+import { useUIStore } from '@/stores/useUIStore';
+import { useSettingsDirectory } from '@/hooks/useSettingsDirectory';
 import { isVSCodeRuntime } from '@/lib/desktop';
 import { cn } from '@/lib/utils';
 import { useI18n } from '@/lib/i18n';
@@ -17,8 +19,11 @@ const formatProjectLabel = (label: string): string => label.trim();
 export const SettingsProjectSelector: React.FC<{ className?: string }> = ({ className }) => {
   const { t } = useI18n();
   const projects = useProjectsStore((state) => state.projects);
-  const activeProjectId = useProjectsStore((state) => state.activeProjectId);
-  const setActiveProject = useProjectsStore((state) => state.setActiveProject);
+  // Settings-only selection. Picking a project here used to call
+  // `setActiveProject`, which relocates the chat, the session list and the file
+  // tree; reading another project's configuration must not move the app.
+  const settingsDirectory = useSettingsDirectory();
+  const setSettingsProjectPath = useUIStore((state) => state.setSettingsProjectPath);
 
   const isVSCode = React.useMemo(() => isVSCodeRuntime(), []);
 
@@ -30,8 +35,8 @@ export const SettingsProjectSelector: React.FC<{ className?: string }> = ({ clas
     if (sortedProjects.length === 0) {
       return null;
     }
-    return sortedProjects.find((p) => p.id === activeProjectId) ?? sortedProjects[0];
-  }, [activeProjectId, sortedProjects]);
+    return sortedProjects.find((p) => p.path === settingsDirectory) ?? sortedProjects[0];
+  }, [settingsDirectory, sortedProjects]);
 
   if (isVSCode || sortedProjects.length === 0) {
     return null;
@@ -67,7 +72,9 @@ export const SettingsProjectSelector: React.FC<{ className?: string }> = ({ clas
             value={activeProject?.id ?? ''}
             onValueChange={(value) => {
               if (!value) return;
-              setActiveProject(value);
+              const project = sortedProjects.find((entry) => entry.id === value);
+              if (!project) return;
+              setSettingsProjectPath(project.path);
             }}
           >
             {sortedProjects.map((project) => {