feat: Add project filter to listInitiatives

Add findByProjectId to InitiativeRepository using a subquery on the
initiative_projects junction table. Extend the listInitiatives tRPC
procedure to accept an optional projectId filter that composes with
the existing status filter. Add a project dropdown to the initiatives
page alongside the status filter.

apps/server/db/repositories/drizzle/initiative.ts

@@ -4,10 +4,10 @@
  * Implements InitiativeRepository interface using Drizzle ORM.
  */
 
-import { eq } from 'drizzle-orm';
+import { eq, inArray } from 'drizzle-orm';
 import { nanoid } from 'nanoid';
 import type { DrizzleDatabase } from '../../index.js';
-import { agents, initiatives, type Initiative } from '../../schema.js';
+import { agents, initiatives, initiativeProjects, type Initiative } from '../../schema.js';
 import type {
   InitiativeRepository,
   CreateInitiativeData,
@@ -59,6 +59,18 @@ export class DrizzleInitiativeRepository implements InitiativeRepository {
       .where(eq(initiatives.status, status));
   }
 
+  async findByProjectId(projectId: string): Promise<Initiative[]> {
+    const linkedIds = this.db
+      .select({ id: initiativeProjects.initiativeId })
+      .from(initiativeProjects)
+      .where(eq(initiativeProjects.projectId, projectId));
+
+    return this.db
+      .select()
+      .from(initiatives)
+      .where(inArray(initiatives.id, linkedIds));
+  }
+
   async update(id: string, data: UpdateInitiativeData): Promise<Initiative> {
     const [updated] = await this.db
       .update(initiatives)

apps/server/db/repositories/initiative-repository.ts

@@ -57,6 +57,12 @@ export interface InitiativeRepository {
    */
   update(id: string, data: UpdateInitiativeData): Promise<Initiative>;
 
+  /**
+   * Find all initiatives linked to a specific project.
+   * Returns empty array if none exist.
+   */
+  findByProjectId(projectId: string): Promise<Initiative[]>;
+
   /**
    * Delete an initiative.
    * Throws if initiative not found.

apps/server/trpc/routers/initiative.ts

@@ -111,12 +111,22 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
     listInitiatives: publicProcedure
       .input(z.object({
         status: z.enum(['active', 'completed', 'archived']).optional(),
+        projectId: z.string().min(1).optional(),
       }).optional())
       .query(async ({ ctx, input }) => {
         const repo = requireInitiativeRepository(ctx);
-        const initiatives = input?.status
-          ? await repo.findByStatus(input.status)
-          : await repo.findAll();
+
+        let initiatives;
+        if (input?.projectId) {
+          const all = await repo.findByProjectId(input.projectId);
+          initiatives = input.status
+            ? all.filter(i => i.status === input.status)
+            : all;
+        } else {
+          initiatives = input?.status
+            ? await repo.findByStatus(input.status)
+            : await repo.findAll();
+        }
 
         // Fetch active architect agents once for all initiatives
         const ARCHITECT_MODES = ['discuss', 'plan', 'detail', 'refine'];