feat: Make initiative branch and execution mode editable from header

- Execution mode badge toggles between YOLO/REVIEW on click
- Branch badge opens inline editor (input + save/cancel)
- Branch editing locked once any task has left pending status
- Server-side guard rejects branch changes after work has started
- getInitiative returns branchLocked flag
- updateInitiativeConfig now accepts optional branch field

src/trpc/routers/initiative.ts

@@ -5,7 +5,7 @@
 import { TRPCError } from '@trpc/server';
 import { z } from 'zod';
 import type { ProcedureBuilder } from '../trpc.js';
-import { requireInitiativeRepository, requireProjectRepository } from './_helpers.js';
+import { requireInitiativeRepository, requireProjectRepository, requireTaskRepository } from './_helpers.js';
 
 export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
   return {
@@ -87,7 +87,13 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
           projects = fullProjects.map((p) => ({ id: p.id, name: p.name, url: p.url }));
         }
 
-        return { ...initiative, projects };
+        let branchLocked = false;
+        if (ctx.taskRepository) {
+          const tasks = await ctx.taskRepository.findByInitiativeId(input.id);
+          branchLocked = tasks.some((t) => t.status !== 'pending');
+        }
+
+        return { ...initiative, projects, branchLocked };
       }),
 
     updateInitiative: publicProcedure
@@ -107,6 +113,7 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
         initiativeId: z.string().min(1),
         mergeRequiresApproval: z.boolean().optional(),
         executionMode: z.enum(['yolo', 'review_per_phase']).optional(),
+        branch: z.string().nullable().optional(),
       }))
       .mutation(async ({ ctx, input }) => {
         const repo = requireInitiativeRepository(ctx);
@@ -120,6 +127,18 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
           });
         }
 
+        // Prevent branch changes once work has started
+        if (data.branch !== undefined && ctx.taskRepository) {
+          const tasks = await ctx.taskRepository.findByInitiativeId(initiativeId);
+          const hasStarted = tasks.some((t) => t.status !== 'pending');
+          if (hasStarted) {
+            throw new TRPCError({
+              code: 'PRECONDITION_FAILED',
+              message: 'Cannot change branch after work has started',
+            });
+          }
+        }
+
         return repo.update(initiativeId, data);
       }),
   };