fix: Prevent conflict resolution agent from destroying initiative branch

spawnConflictResolutionAgent was passing the initiative branch as branchName,
causing SimpleGitWorktreeManager.create() to force-reset it to the target
branch. Now spawns on a unique temp branch based off the initiative branch,
with the agent using git update-ref to advance the initiative branch after
resolving conflicts. Also fixes stale diff/commits cache after resolution.

apps/server/trpc/routers/initiative.ts

@@ -459,7 +459,10 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
           status: 'in_progress',
         });
 
-        // Spawn agent
+        // Spawn agent on a unique temp branch based off the initiative branch.
+        // Using initiative.branch directly as branchName would cause SimpleGitWorktreeManager.create()
+        // to run `git branch -f <branch> <base>`, force-resetting the initiative branch.
+        const tempBranch = `${initiative.branch}-conflict-${Date.now()}`;
         const prompt = buildConflictResolutionPrompt(initiative.branch, targetBranch, conflicts);
         return agentManager.spawn({
           name: `conflict-${Date.now()}`,
@@ -468,8 +471,8 @@ export function initiativeProcedures(publicProcedure: ProcedureBuilder) {
           mode: 'execute',
           provider: input.provider,
           initiativeId: input.initiativeId,
-          baseBranch: targetBranch,
-          branchName: initiative.branch,
+          baseBranch: initiative.branch,
+          branchName: tempBranch,
         });
       }),
   };