feat: Sprint 4 — scenario planner, report builder, comments, dashboard widgets

What-If Scenario Planner (G5):
- New /projects/[id]/scenario page with side-by-side baseline vs scenario
- simulate mutation: pure cost/hours/headcount/utilization computation
- apply mutation: creates real PROPOSED assignments from scenario
- Impact cards: cost delta, hours delta, headcount, skill coverage %
- Per-resource utilization impact table with over-allocation warnings
- "What-If" button added to project detail page

Custom Report Builder (G7):
- New /reports/builder page with full config panel
- Entity selector (resource/project/assignment), column picker, filter builder
- Dynamic Prisma query with eq/neq/gt/lt/contains/in operators
- Sortable results table with pagination (50/page)
- CSV export via exportReport mutation
- Sidebar nav link under Analytics

Collaboration Layer (G8):
- Comment model in Prisma (entityType/entityId, replies, @mentions, resolved)
- comment router: list, count, create, resolve, delete
- @mention parsing with notification creation + SSE delivery
- CommentInput with @mention autocomplete (arrow nav, Enter/Tab confirm)
- CommentThread with avatar, timestamp, reply, resolve, delete
- Integrated as "Comments" tab in estimate workspace with count badge

Dashboard Widgets:
- BudgetForecastWidget: progress bars per project, burn rate, exhaustion date
- SkillGapWidget: supply vs demand per skill, shortage/surplus indicators
- ProjectHealthWidget: 3-dimension health circles + composite score
- 3 new application use-cases + dashboard router queries
- All registered in widget-registry with lazy imports

Co-Authored-By: claude-flow <ruv@ruv.net>

packages/api/src/router/dashboard.ts

@@ -6,6 +6,9 @@ import {
   getDashboardOverview,
   getDashboardPeakTimes,
   getDashboardTopValueResources,
+  getDashboardBudgetForecast,
+  getDashboardSkillGaps,
+  getDashboardProjectHealth,
 } from "@planarchy/application";
 import { anonymizeResources, getAnonymizationDirectory } from "../lib/anonymization.js";
 import { cacheGet, cacheSet } from "../lib/cache.js";
@@ -129,4 +132,34 @@ export const dashboardRouter = createTRPCRouter({
       await cacheSet(cacheKey, result, DEFAULT_TTL);
       return result;
     }),
+
+  getBudgetForecast: protectedProcedure.query(async ({ ctx }) => {
+    const cacheKey = "budgetForecast";
+    const cached = await cacheGet<Awaited<ReturnType<typeof getDashboardBudgetForecast>>>(cacheKey);
+    if (cached) return cached;
+
+    const result = await getDashboardBudgetForecast(ctx.db);
+    await cacheSet(cacheKey, result, DEFAULT_TTL);
+    return result;
+  }),
+
+  getSkillGaps: protectedProcedure.query(async ({ ctx }) => {
+    const cacheKey = "skillGaps";
+    const cached = await cacheGet<Awaited<ReturnType<typeof getDashboardSkillGaps>>>(cacheKey);
+    if (cached) return cached;
+
+    const result = await getDashboardSkillGaps(ctx.db);
+    await cacheSet(cacheKey, result, DEFAULT_TTL);
+    return result;
+  }),
+
+  getProjectHealth: protectedProcedure.query(async ({ ctx }) => {
+    const cacheKey = "projectHealth";
+    const cached = await cacheGet<Awaited<ReturnType<typeof getDashboardProjectHealth>>>(cacheKey);
+    if (cached) return cached;
+
+    const result = await getDashboardProjectHealth(ctx.db);
+    await cacheSet(cacheKey, result, DEFAULT_TTL);
+    return result;
+  }),
 });