fix(zfc): remove Go-side computation and stderr parsing violations

hq-u0ach: done.go - Add --cleanup-status flag so agents can pass cleanup
status directly. Removes computeCleanupStatus() which violated ZFC by
having Go compute cleanup status from git state.

hq-z0zqw: beads.go - Remove strings.Contains parsing for ErrNotARepo and
ErrSyncConflict. Per ZFC, Go should transport errors to agents, not parse
them to make decisions. IsBeadsRepo() now uses file existence check.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/beads/beads_test.go

@@ -84,6 +84,8 @@ func TestIsBeadsRepo(t *testing.T) {
 }
 
 // TestWrapError tests error wrapping.
+// ZFC: Only test ErrNotFound detection. ErrNotARepo and ErrSyncConflict
+// were removed as per ZFC - agents should handle those errors directly.
 func TestWrapError(t *testing.T) {
 	b := New("/test")
 
@@ -92,11 +94,6 @@ func TestWrapError(t *testing.T) {
 		wantErr error
 		wantNil bool
 	}{
-		{"not a beads repository", ErrNotARepo, false},
-		{"No .beads directory found", ErrNotARepo, false},
-		{".beads directory not found", ErrNotARepo, false},
-		{"sync conflict detected", ErrSyncConflict, false},
-		{"CONFLICT in file.md", ErrSyncConflict, false},
 		{"Issue not found: gt-xyz", ErrNotFound, false},
 		{"gt-xyz not found", ErrNotFound, false},
 	}