feat(FN-4313): complete Step 1 — add central default project setting

Fusion-Task-Id: FN-4313
Fusion-Task-Lineage: 36b8aad3-20f4-475b-9b0f-63e5458d1b91

packages/core/src/__tests__/central-core.test.ts

@@ -2378,6 +2378,58 @@ describe("CentralCore", () => {
     });
   });
 
+  describe("default project setting", () => {
+    beforeEach(async () => {
+      await central.init();
+    });
+
+    it("should be undefined by default", async () => {
+      await expect(central.getDefaultProjectId()).resolves.toBeUndefined();
+    });
+
+    it("should set/get and clear default project id", async () => {
+      const projectPath = join(tempDir, "default-project");
+      mkdirSync(projectPath);
+      projectPaths.push(projectPath);
+
+      const project = await central.registerProject({
+        name: "Default Project",
+        path: projectPath,
+      });
+
+      await central.setDefaultProjectId(project.id);
+      await expect(central.getDefaultProjectId()).resolves.toBe(project.id);
+
+      await central.setDefaultProjectId(null);
+      await expect(central.getDefaultProjectId()).resolves.toBeUndefined();
+    });
+
+    it("should reject unknown project id", async () => {
+      await expect(central.setDefaultProjectId("missing-project-id")).rejects.toThrow(
+        "Cannot set default project: project not found: missing-project-id",
+      );
+    });
+
+    it("should persist setting across reopen", async () => {
+      const projectPath = join(tempDir, "persisted-default-project");
+      mkdirSync(projectPath);
+      projectPaths.push(projectPath);
+
+      const project = await central.registerProject({
+        name: "Persisted Default Project",
+        path: projectPath,
+      });
+
+      await central.setDefaultProjectId(project.id);
+      await central.close();
+
+      central = new CentralCore(tempDir);
+      await central.init();
+
+      await expect(central.getDefaultProjectId()).resolves.toBe(project.id);
+    });
+  });
+
   describe("global concurrency", () => {
     beforeEach(async () => {
       await central.init();

packages/core/src/central-core.ts

@@ -2424,6 +2424,31 @@ export class CentralCore extends EventEmitter<CentralCoreEvents> {
     return deletedCount;
   }
 
+  async getDefaultProjectId(): Promise<string | undefined> {
+    this.ensureInitialized();
+
+    const row = this.db!.prepare("SELECT defaultProjectId FROM centralSettings WHERE id = 1").get() as
+      | { defaultProjectId: string | null }
+      | undefined;
+
+    return row?.defaultProjectId ?? undefined;
+  }
+
+  async setDefaultProjectId(projectId: string | null): Promise<void> {
+    this.ensureInitialized();
+
+    if (projectId !== null) {
+      const project = await this.getProject(projectId);
+      if (!project) {
+        throw new Error(`Cannot set default project: project not found: ${projectId}`);
+      }
+    }
+
+    this.db!
+      .prepare("UPDATE centralSettings SET defaultProjectId = ?, updatedAt = ? WHERE id = 1")
+      .run(projectId, new Date().toISOString());
+  }
+
   // ── Global Concurrency API ─────────────────────────────────────────────
 
   /**

packages/core/src/central-db.ts

@@ -29,7 +29,7 @@ export { toJson, toJsonNullable, fromJson };
 
 // ── Schema Definition ───────────────────────────────────────────────────
 
-const CENTRAL_SCHEMA_VERSION = 10;
+const CENTRAL_SCHEMA_VERSION = 11;
 
 const CENTRAL_SCHEMA_SQL = `
 -- Projects table (project registry)
@@ -107,6 +107,15 @@ CREATE TABLE IF NOT EXISTS globalConcurrency (
 INSERT OR IGNORE INTO globalConcurrency (id, globalMaxConcurrent, currentlyActive, queuedCount) 
 VALUES (1, 4, 0, 0);
 
+-- Central settings (single row)
+CREATE TABLE IF NOT EXISTS centralSettings (
+  id INTEGER PRIMARY KEY CHECK (id = 1),
+  defaultProjectId TEXT,
+  updatedAt TEXT NOT NULL
+);
+INSERT OR IGNORE INTO centralSettings (id, defaultProjectId, updatedAt)
+VALUES (1, NULL, CURRENT_TIMESTAMP);
+
 -- Nodes table (runtime hosts for project execution)
 CREATE TABLE IF NOT EXISTS nodes (
   id TEXT PRIMARY KEY,
@@ -433,6 +442,16 @@ CREATE TABLE IF NOT EXISTS meshWriteQueue (
 CREATE INDEX IF NOT EXISTS idxMeshWriteQueueReplay ON meshWriteQueue(targetNodeId, status, createdAt, id);
 `;
 
+const CENTRAL_SCHEMA_V11_MIGRATION_SQL = `
+CREATE TABLE IF NOT EXISTS centralSettings (
+  id INTEGER PRIMARY KEY CHECK (id = 1),
+  defaultProjectId TEXT,
+  updatedAt TEXT NOT NULL
+);
+INSERT OR IGNORE INTO centralSettings (id, defaultProjectId, updatedAt)
+VALUES (1, NULL, CURRENT_TIMESTAMP);
+`;
+
 // ── Central Database Class ────────────────────────────────────────────────
 
 export class CentralDatabase {
@@ -575,6 +594,11 @@ export class CentralDatabase {
       migrated = true;
     }
 
+    if (currentVersion < 11) {
+      this.db.exec(CENTRAL_SCHEMA_V11_MIGRATION_SQL);
+      migrated = true;
+    }
+
     if (migrated) {
       this.db
         .prepare("INSERT INTO __meta (key, value) VALUES ('schemaVersion', ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value")