feat: split getPhaseReviewDiff into metadata + add getFileDiff procedure

Rewrites getPhaseReviewDiff to return file-level metadata (path, status,
additions, deletions) instead of a raw diff string, eliminating 10MB+
payloads for large repos. Adds getFileDiff for on-demand per-file hunk
content with binary detection via numstat. Multi-project initiatives
prefix file paths with the project name to avoid collisions.

Adds integration tests that use real local git repos + in-memory SQLite
to verify both procedures end-to-end (binary files, deleted files,
spaces in paths, error cases).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/server/trpc/routers/phase.ts

@@ -4,11 +4,13 @@
 
 import { TRPCError } from '@trpc/server';
 import { z } from 'zod';
+import { simpleGit } from 'simple-git';
 import type { Phase } from '../../db/schema.js';
 import type { ProcedureBuilder } from '../trpc.js';
 import { requirePhaseRepository, requireTaskRepository, requireBranchManager, requireInitiativeRepository, requireProjectRepository, requireExecutionOrchestrator, requireReviewCommentRepository, requireChangeSetRepository } from './_helpers.js';
 import { phaseBranchName } from '../../git/branch-naming.js';
 import { ensureProjectClone } from '../../git/project-clones.js';
+import type { FileStatEntry } from '../../git/types.js';
 
 export function phaseProcedures(publicProcedure: ProcedureBuilder) {
   return {
@@ -230,28 +232,93 @@ export function phaseProcedures(publicProcedure: ProcedureBuilder) {
 
         const initBranch = initiative.branch;
         const phBranch = phaseBranchName(initBranch, phase.name);
-        // For completed phases, use stored merge base; for pending_review, use initiative branch
         const diffBase = (phase.status === 'completed' && phase.mergeBase) ? phase.mergeBase : initBranch;
 
         const projects = await projectRepo.findProjectsByInitiativeId(phase.initiativeId);
-        let rawDiff = '';
+        const files: FileStatEntry[] = [];
 
         for (const project of projects) {
           const clonePath = await ensureProjectClone(project, ctx.workspaceRoot!);
-          const diff = await branchManager.diffBranches(clonePath, diffBase, phBranch);
-          if (diff) {
-            rawDiff += diff + '\n';
+          const entries = await branchManager.diffBranchesStat(clonePath, diffBase, phBranch);
+          for (const entry of entries) {
+            const tagged: FileStatEntry = { ...entry, projectId: project.id };
+            if (projects.length > 1) {
+              tagged.path = `${project.name}/${entry.path}`;
+              if (entry.oldPath) {
+                tagged.oldPath = `${project.name}/${entry.oldPath}`;
+              }
+            }
+            files.push(tagged);
           }
         }
 
+        const totalAdditions = files.reduce((sum, f) => sum + f.additions, 0);
+        const totalDeletions = files.reduce((sum, f) => sum + f.deletions, 0);
+
         return {
           phaseName: phase.name,
           sourceBranch: phBranch,
           targetBranch: initBranch,
-          rawDiff,
+          files,
+          totalAdditions,
+          totalDeletions,
         };
       }),
 
+    getFileDiff: publicProcedure
+      .input(z.object({
+        phaseId: z.string().min(1),
+        filePath: z.string().min(1),
+        projectId: z.string().optional(),
+      }))
+      .query(async ({ ctx, input }) => {
+        const phaseRepo = requirePhaseRepository(ctx);
+        const initiativeRepo = requireInitiativeRepository(ctx);
+        const projectRepo = requireProjectRepository(ctx);
+        const branchManager = requireBranchManager(ctx);
+
+        const phase = await phaseRepo.findById(input.phaseId);
+        if (!phase) {
+          throw new TRPCError({ code: 'NOT_FOUND', message: `Phase '${input.phaseId}' not found` });
+        }
+        if (phase.status !== 'pending_review' && phase.status !== 'completed') {
+          throw new TRPCError({ code: 'BAD_REQUEST', message: `Phase is not reviewable (status: ${phase.status})` });
+        }
+
+        const initiative = await initiativeRepo.findById(phase.initiativeId);
+        if (!initiative?.branch) {
+          throw new TRPCError({ code: 'BAD_REQUEST', message: 'Initiative has no branch configured' });
+        }
+
+        const initBranch = initiative.branch;
+        const phBranch = phaseBranchName(initBranch, phase.name);
+        const diffBase = (phase.status === 'completed' && phase.mergeBase) ? phase.mergeBase : initBranch;
+
+        const decodedPath = decodeURIComponent(input.filePath);
+
+        const projects = await projectRepo.findProjectsByInitiativeId(phase.initiativeId);
+        let clonePath: string;
+        if (input.projectId) {
+          const project = projects.find((p) => p.id === input.projectId);
+          if (!project) {
+            throw new TRPCError({ code: 'NOT_FOUND', message: `Project '${input.projectId}' not found for this phase` });
+          }
+          clonePath = await ensureProjectClone(project, ctx.workspaceRoot!);
+        } else {
+          clonePath = await ensureProjectClone(projects[0], ctx.workspaceRoot!);
+        }
+
+        const git = simpleGit(clonePath);
+        // Binary files appear as "-\t-\t<path>" in --numstat output
+        const numstatOut = await git.raw(['diff', '--numstat', `${diffBase}...${phBranch}`, '--', decodedPath]);
+        if (numstatOut.trim() && numstatOut.startsWith('-\t-\t')) {
+          return { binary: true, rawDiff: '' };
+        }
+
+        const rawDiff = await branchManager.diffFileSingle(clonePath, diffBase, phBranch, decodedPath);
+        return { binary: false, rawDiff };
+      }),
+
     approvePhaseReview: publicProcedure
       .input(z.object({ phaseId: z.string().min(1) }))
       .mutation(async ({ ctx, input }) => {