Add "(no output)" fallback to all git error messages

The helpers already handled empty stderr but the git module did not,
leading to confusing error messages with a trailing colon and no detail.

src/commands/helpers.ts

@@ -128,7 +128,7 @@ export async function resolveConflicts(
     )
 
     if (resolved.exitCode !== 0) {
-      const stderr = resolved.stderr.toString().trim()
+      const stderr = resolved.stderr.trim()
       throw new Error(`Claude failed to resolve ${file}: ${stderr || "(no output)"}`)
     }
 

src/git.ts

@@ -72,7 +72,8 @@ export async function createWorktree(branch: string, worktreePath: string, cwd:
   }
   if (result.exitCode !== 0) {
     if (switchedFromBranch) await checkout(branch, cwd).catch(() => {})
-    throw new Error(`Failed to create worktree for "${branch}": ${result.stderr.toString().trim()}`)
+    const stderr = result.stderr.toString().trim()
+    throw new Error(`Failed to create worktree for "${branch}": ${stderr || "(no output)"}`)
   }
   return { branchCreated: exists !== "local" }
 }
@@ -98,7 +99,8 @@ export async function deleteLocalBranch(branch: string, cwd: string): Promise<vo
 export async function checkout(branch: string, cwd: string): Promise<void> {
   const result = await $`git checkout ${branch}`.cwd(cwd).nothrow().quiet()
   if (result.exitCode !== 0) {
-    throw new Error(`Failed to checkout branch "${branch}": ${result.stderr.toString().trim()}`)
+    const stderr = result.stderr.toString().trim()
+    throw new Error(`Failed to checkout branch "${branch}": ${stderr || "(no output)"}`)
   }
 }
 
@@ -117,7 +119,8 @@ export async function merge(branch: string, cwd: string, opts?: { squash?: boole
 
   // Not a conflict — some other merge failure
   const label = opts?.squash ? "squash-merge" : "merge"
-  throw new Error(`Failed to ${label} branch "${branch}": ${result.stderr.toString().trim()}`)
+  const stderr = result.stderr.toString().trim()
+  throw new Error(`Failed to ${label} branch "${branch}": ${stderr || "(no output)"}`)
 }
 
 /** Return the staged diff as text. */
@@ -129,7 +132,8 @@ export async function diffStaged(cwd: string): Promise<string> {
 export async function commit(message: string, cwd: string): Promise<void> {
   const result = await $`git commit -m ${message}`.cwd(cwd).nothrow().quiet()
   if (result.exitCode !== 0) {
-    throw new Error(`Failed to commit: ${result.stderr.toString().trim()}`)
+    const stderr = result.stderr.toString().trim()
+    throw new Error(`Failed to commit: ${stderr || "(no output)"}`)
   }
 }
 
@@ -155,7 +159,8 @@ export async function stageFile(file: string, cwd: string): Promise<void> {
 export async function commitMerge(cwd: string): Promise<void> {
   const result = await $`git commit --no-edit`.cwd(cwd).nothrow().quiet()
   if (result.exitCode !== 0) {
-    throw new Error(`Failed to commit merge: ${result.stderr.toString().trim()}`)
+    const stderr = result.stderr.toString().trim()
+    throw new Error(`Failed to commit merge: ${stderr || "(no output)"}`)
   }
 }
 
@@ -193,7 +198,8 @@ export async function rebaseContinue(cwd: string): Promise<string[]> {
   const files = unmerged.trim().split("\n").filter(Boolean)
   if (files.length > 0) return files
 
-  throw new Error(`Rebase --continue failed: ${result.stderr.toString().trim()}`)
+  const stderr = result.stderr.toString().trim()
+  throw new Error(`Rebase --continue failed: ${stderr || "(no output)"}`)
 }
 
 /** Abort an in-progress rebase. */