go.mod specified go 1.25.6 which triggered automatic toolchain download
via Go's toolchain management. Go 1.25 removed the covdata tool, causing
the CI test step to fail with 'go: no such tool covdata'.
Changes:
- go.mod: downgrade 'go 1.25.6' to 'go 1.24' to match CI setup-go version
- ci.yml: add GOTOOLCHAIN=local env at job level to prevent auto-download
of newer toolchain versions
Fixes CI failure on main branch.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: multica-agent <github@multica.ai>