issue: #50764
The `2.6` branch CI is currently failing to compile (`build-go`) at
`cce25693c6`:
```
internal/datacoord/task_index.go:332:41: undefined: fmt
internal/datacoord/task_index.go:355:41: undefined: fmt
make: *** [Makefile:113: build-go] Error 1
```
### Root cause — merge-order conflict
- #50545 (merr error-handling standardization) replaced every `fmt.*`
use in `task_index.go` with `merr.*` and dropped the then-unused `fmt`
import.
- #50727 (ArrayOfVector EmbList indexes) then added two new
`fmt.Sprintf` calls but did not re-add the `fmt` import.
Each PR compiled in isolation, but the merged tree did not. This is the
same class of failure as #50756.
### Fix
Re-add the `fmt` import to `internal/datacoord/task_index.go`,
unblocking the 2.6 branch build. `gofmt` clean; the import has two real
usages so it is not unused.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Signed-off-by: Li Liu <li.liu@zilliz.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>