chore(ci): add govulncheck, staticcheck, go vet, gofumpt gates

* Add lint/format checks to the Gitea release workflow and Makefile
  (targets: vet, fmt, fmt-check, staticcheck, govulncheck, check)
* Switch .golangci.json formatter from gofmt to gofumpt (extra.group-params)
* Bump golang.org/x/text 0.37.0 -> 0.39.0 for GO-2026-5970; re-vendor
* Fix staticcheck S1011 in pkg/diff; drop unused pgsql writer helpers
* Fix gocritic unnamedResult (pkg/diff) and rangeValCopy (pkg/pgsql)
* Apply gofumpt + goimports formatting across the tree

vendor/golang.org/x/sys/unix/syscall_openbsd.go

@@ -300,6 +300,10 @@ func Uname(uname *Utsname) error {
 //sys	Pathconf(path string, name int) (val int, err error)
 //sys	pread(fd int, p []byte, offset int64) (n int, err error)
 //sys	pwrite(fd int, p []byte, offset int64) (n int, err error)
+//sys	readv(fd int, iovecs []Iovec) (n int, err error)
+//sys	writev(fd int, iovecs []Iovec) (n int, err error)
+//sys	preadv(fd int, iovecs []Iovec, offset int64) (n int, err error)
+//sys	pwritev(fd int, iovecs []Iovec, offset int64) (n int, err error)
 //sys	read(fd int, p []byte) (n int, err error)
 //sys	Readlink(path string, buf []byte) (n int, err error)
 //sys	Readlinkat(dirfd int, path string, buf []byte) (n int, err error)