feat: Add merge conflict detection and agent resolution in initiative review

Pre-merge mergeability check via `git merge-tree --write-tree` (dry-run, no
side effects). When conflicts exist the "Merge & Push" button is disabled and
a ConflictResolutionPanel shows conflict files with options to resolve manually
or spawn a conflict-resolution agent. Agent questions appear inline via
QuestionForm; on completion the mergeability re-checks automatically.

New server-side: MergeabilityResult type, BranchManager.checkMergeability,
conflict-resolution prompt, checkInitiativeMergeability query,
spawnConflictResolutionAgent mutation, getActiveConflictAgent query.

New frontend: useConflictAgent hook, ConflictResolutionPanel component,
mergeability badge + panel integration in InitiativeReview.

apps/server/trpc/routers/agent.ts

@@ -184,6 +184,27 @@ export function agentProcedures(publicProcedure: ProcedureBuilder) {
         return candidates[0] ?? null;
       }),
 
+    getActiveConflictAgent: publicProcedure
+      .input(z.object({ initiativeId: z.string().min(1) }))
+      .query(async ({ ctx, input }): Promise<AgentInfo | null> => {
+        const agentManager = requireAgentManager(ctx);
+        const allAgents = await agentManager.list();
+        const candidates = allAgents
+          .filter(
+            (a) =>
+              a.mode === 'execute' &&
+              a.initiativeId === input.initiativeId &&
+              a.name?.startsWith('conflict-') &&
+              ['running', 'waiting_for_input', 'idle', 'crashed'].includes(a.status) &&
+              !a.userDismissedAt,
+          )
+          .sort(
+            (a, b) =>
+              new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime(),
+          );
+        return candidates[0] ?? null;
+      }),
+
     getAgentOutput: publicProcedure
       .input(agentIdentifierSchema)
       .query(async ({ ctx, input }): Promise<string> => {

apps/server/trpc/routers/initiative.ts

@@ -7,7 +7,7 @@ import { z } from 'zod';
 import type { ProcedureBuilder } from '../trpc.js';
 import { requireAgentManager, requireInitiativeRepository, requireProjectRepository, requireTaskRepository, requireBranchManager, requireExecutionOrchestrator } from './_helpers.js';
 import { deriveInitiativeActivity } from './initiative-activity.js';
-import { buildRefinePrompt } from '../../agent/prompts/index.js';
+import { buildRefinePrompt, buildConflictResolutionPrompt, buildConflictResolutionDescription } from '../../agent/prompts/index.js';
 import type { PageForSerialization } from '../../agent/content-serializer.js';
 import { ensureProjectClone } from '../../git/project-clones.js';
 
@@ -349,5 +349,128 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
         );
         return { success: true, taskId: result.taskId };
       }),
+
+    checkInitiativeMergeability: publicProcedure
+      .input(z.object({ initiativeId: z.string().min(1) }))
+      .query(async ({ ctx, input }) => {
+        const initiativeRepo = requireInitiativeRepository(ctx);
+        const projectRepo = requireProjectRepository(ctx);
+        const branchManager = requireBranchManager(ctx);
+
+        const initiative = await initiativeRepo.findById(input.initiativeId);
+        if (!initiative) {
+          throw new TRPCError({ code: 'NOT_FOUND', message: `Initiative '${input.initiativeId}' not found` });
+        }
+        if (!initiative.branch) {
+          throw new TRPCError({ code: 'BAD_REQUEST', message: 'Initiative has no branch configured' });
+        }
+
+        const projects = await projectRepo.findProjectsByInitiativeId(input.initiativeId);
+        const allConflicts: string[] = [];
+        let mergeable = true;
+
+        for (const project of projects) {
+          const clonePath = await ensureProjectClone(project, ctx.workspaceRoot!);
+          const result = await branchManager.checkMergeability(clonePath, initiative.branch, project.defaultBranch);
+          if (!result.mergeable) {
+            mergeable = false;
+            if (result.conflicts) allConflicts.push(...result.conflicts);
+          }
+        }
+
+        return {
+          mergeable,
+          conflictFiles: allConflicts,
+          targetBranch: projects[0]?.defaultBranch ?? 'main',
+        };
+      }),
+
+    spawnConflictResolutionAgent: publicProcedure
+      .input(z.object({
+        initiativeId: z.string().min(1),
+        provider: z.string().optional(),
+      }))
+      .mutation(async ({ ctx, input }) => {
+        const agentManager = requireAgentManager(ctx);
+        const initiativeRepo = requireInitiativeRepository(ctx);
+        const projectRepo = requireProjectRepository(ctx);
+        const taskRepo = requireTaskRepository(ctx);
+        const branchManager = requireBranchManager(ctx);
+
+        const initiative = await initiativeRepo.findById(input.initiativeId);
+        if (!initiative) {
+          throw new TRPCError({ code: 'NOT_FOUND', message: `Initiative '${input.initiativeId}' not found` });
+        }
+        if (!initiative.branch) {
+          throw new TRPCError({ code: 'BAD_REQUEST', message: 'Initiative has no branch configured' });
+        }
+
+        const projects = await projectRepo.findProjectsByInitiativeId(input.initiativeId);
+        if (projects.length === 0) {
+          throw new TRPCError({ code: 'BAD_REQUEST', message: 'Initiative has no linked projects' });
+        }
+
+        // Auto-dismiss stale conflict agents
+        const allAgents = await agentManager.list();
+        const staleAgents = allAgents.filter(
+          (a) =>
+            a.mode === 'execute' &&
+            a.initiativeId === input.initiativeId &&
+            a.name?.startsWith('conflict-') &&
+            ['crashed', 'idle'].includes(a.status) &&
+            !a.userDismissedAt,
+        );
+        for (const stale of staleAgents) {
+          await agentManager.dismiss(stale.id);
+        }
+
+        // Reject if active conflict agent already running
+        const activeConflictAgents = allAgents.filter(
+          (a) =>
+            a.mode === 'execute' &&
+            a.initiativeId === input.initiativeId &&
+            a.name?.startsWith('conflict-') &&
+            ['running', 'waiting_for_input'].includes(a.status),
+        );
+        if (activeConflictAgents.length > 0) {
+          throw new TRPCError({
+            code: 'CONFLICT',
+            message: 'A conflict resolution agent is already running for this initiative',
+          });
+        }
+
+        // Re-check mergeability to get current conflict list
+        const project = projects[0];
+        const clonePath = await ensureProjectClone(project, ctx.workspaceRoot!);
+        const mergeCheck = await branchManager.checkMergeability(clonePath, initiative.branch, project.defaultBranch);
+        if (mergeCheck.mergeable) {
+          throw new TRPCError({ code: 'BAD_REQUEST', message: 'No merge conflicts detected — merge is clean' });
+        }
+
+        const conflicts = mergeCheck.conflicts ?? [];
+        const targetBranch = project.defaultBranch;
+
+        // Create task
+        const task = await taskRepo.create({
+          initiativeId: input.initiativeId,
+          name: `Resolve conflicts: ${initiative.name}`,
+          description: buildConflictResolutionDescription(initiative.branch, targetBranch, conflicts),
+          category: 'merge',
+          status: 'in_progress',
+        });
+
+        // Spawn agent
+        const prompt = buildConflictResolutionPrompt(initiative.branch, targetBranch, conflicts);
+        return agentManager.spawn({
+          name: `conflict-${Date.now()}`,
+          taskId: task.id,
+          prompt,
+          mode: 'execute',
+          provider: input.provider,
+          initiativeId: input.initiativeId,
+          baseBranch: targetBranch,
+          branchName: initiative.branch,
+        });
+      }),
   };
 }