fix: reject project belonging to multiple workspaces

Validate during config parsing that each project appears in at most
one workspace. Previously the last workspace silently won, causing
the project's data to end up in the wrong DB.

Author: prih

src/lib/multi-config.ts

@@ -594,12 +594,18 @@ export function loadMultiConfig(yamlPath: string): MultiConfig {
   // --- Workspaces ---
   const workspaces = new Map<string, WorkspaceConfig>();
 
+  const projectToWorkspace = new Map<string, string>();
   if (validated.workspaces) {
     for (const [wsId, raw] of Object.entries(validated.workspaces)) {
       for (const projId of raw.projects) {
         if (!projects.has(projId)) {
           throw new Error(`Workspace "${wsId}" references unknown project "${projId}"`);
         }
+        const existing = projectToWorkspace.get(projId);
+        if (existing) {
+          throw new Error(`Project "${projId}" belongs to multiple workspaces: "${existing}" and "${wsId}"`);
+        }
+        projectToWorkspace.set(projId, wsId);
       }
 
       const firstProject = projects.get(raw.projects[0])!;

src/tests/multi-config.test.ts

@@ -352,6 +352,24 @@ workspaces:
     expect(() => loadMultiConfig(yamlPath)).toThrow('unknown project "nonexistent"');
   });
 
+  it('throws when project belongs to multiple workspaces', () => {
+    const yamlPath = tmpYaml(`
+projects:
+  a:
+    projectDir: /tmp/a
+  b:
+    projectDir: /tmp/b
+workspaces:
+  ws1:
+    projects: [a]
+    graphMemory: /tmp/ws1
+  ws2:
+    projects: [a, b]
+    graphMemory: /tmp/ws2
+`);
+    expect(() => loadMultiConfig(yamlPath)).toThrow('multiple workspaces: "ws1" and "ws2"');
+  });
+
   it('workspace defaults graphMemory to first project dir', () => {
     const yamlPath = tmpYaml(`
 projects: