fix: support upstream workspace CI partition

scripts/__tests__/run-vitest-stable-shard.test.mjs

@@ -107,9 +107,17 @@ test("general shards retain scripts and route-named suites outside the serialize
   ]) assert.ok(general.selectedGeneralServerSuites.includes(file), `missing configured server suite: ${file}`);
 });
 
-test("shard flags are rejected for the workspaces-b group", () => {
-  const result = dryRun(["--mode", "general", "--group", "general-workspaces-b", "--shard-index", "0", "--shard-count", "3"]);
-  assert.notEqual(result.status, 0, "workspaces-b must not accept shard flags");
+for (const group of ["general-workspaces-b", "general-workspaces-c"]) {
+  test(`shard flags are rejected for the ${group} group`, () => {
+    const result = dryRun(["--mode", "general", "--group", group, "--shard-index", "0", "--shard-count", "3"]);
+    assert.notEqual(result.status, 0, `${group} must not accept shard flags`);
+  });
+}
+
+test("workspaces-c selects only the db project", () => {
+  const selected = dryRunJson(["--mode", "general", "--group", "general-workspaces-c"]);
+  assert.deepEqual(selected.workspaceProjects, ["@paperclipai/db"]);
+  assert.equal(selected.workspacesVitestShard, null);
 });
 
 test("workspace lanes cover every non-server project in the root Vitest configuration", () => {
@@ -118,7 +126,7 @@ test("workspace lanes cover every non-server project in the root Vitest configur
   assert.ok(roots.includes("server"), "expected the explicit root Vitest project list");
   const expected = roots.filter(root => root !== "server")
     .map(root => JSON.parse(readFileSync(path.join(repoRoot, root, "package.json"), "utf8")).name).sort();
-  const actual = ["general-workspaces-a", "general-workspaces-b"]
+  const actual = ["general-workspaces-a", "general-workspaces-b", "general-workspaces-c"]
     .flatMap(group => dryRunJson(["--mode", "general", "--group", group]).workspaceProjects).sort();
   assert.deepEqual(actual, expected, "no configured project may be silently omitted or run twice");
 });

scripts/run-vitest-stable.mjs

@@ -117,9 +117,27 @@ function excludedServerSuites(groupName) {
 }
 const generalWorkspacesAGroupName = "general-workspaces-a";
 const generalWorkspacesBGroupName = "general-workspaces-b";
+const generalWorkspacesCGroupName = "general-workspaces-c";
 const generalWorkspacesAProjects = ["@paperclipai/ui", "paperclipai"];
-const generalWorkspacesBProjects = nonServerProjects.filter((project) => !generalWorkspacesAProjects.includes(project));
-const generalGroupNames = [generalServerGroupName, generalWorkspacesAGroupName, generalWorkspacesBGroupName];
+// The db project runs in its own lane. Its vitest invocation took 168-250s
+// of a 436-513s workspaces-b job (PR runs 38084171761, 38083084276 and
+// 38083020834, 2026-10-10), which made workspaces-b the slowest check once
+// the server shards were rebalanced. Vitest's native --shard would not help
+// here: the project is already file-parallel and client.test.ts alone is
+// 117-189s of its wall time, so a hash-ordered slice can land both of its
+// slow suites on one runner. Splitting by project is deterministic and
+// leaves the remaining projects at ~265-275s of vitest time, roughly level
+// with this lane.
+const generalWorkspacesCProjects = ["@paperclipai/db"];
+const generalWorkspacesBProjects = nonServerProjects.filter(
+  (project) => !generalWorkspacesAProjects.includes(project) && !generalWorkspacesCProjects.includes(project),
+);
+const generalGroupNames = [
+  generalServerGroupName,
+  generalWorkspacesAGroupName,
+  generalWorkspacesBGroupName,
+  generalWorkspacesCGroupName,
+];
 const allowedGeneralGroupNames = [
   ...generalGroupNames,
   generalServerWithoutChatGroupName,
@@ -520,6 +538,11 @@ function runGeneralGroup(routeTests, groupName, shardIndex = null, shardCount =
     return;
   }
 
+  if (groupName === generalWorkspacesCGroupName) {
+    runProjectGroup(generalWorkspacesCProjects, groupName);
+    return;
+  }
+
   fail(`Unknown group "${groupName}".`);
 }
 
@@ -604,7 +627,9 @@ if (options.dryRun) {
             ? generalWorkspacesAProjects
             : options.group === generalWorkspacesBGroupName
               ? generalWorkspacesBProjects
-              : null,
+              : options.group === generalWorkspacesCGroupName
+                ? generalWorkspacesCProjects
+                : null,
         workspacesVitestShard:
           options.group === generalWorkspacesAGroupName &&
           options.shardCount !== null &&