fix(cli/task): run recursive workspace tasks in parallel (#34512)
`deno task -r <name>` (and `deno task --filter <pattern> <name>`)
walked workspace members one at a time, so a long-running task in the
first matched member blocked every other member from starting. This was
especially painful for the common dev-server case described in #27586,
where running `dev` recursively across an `apps/server` + `apps/web`
workspace would only ever boot one of them.
The fix flattens all matched packages' resolved tasks into a single
topology and runs them through the existing parallel task runner, so
cross-package siblings execute concurrently while intra-package task
dependencies still order correctly. When concurrent tasks span more
than one workspace member, the colored output prefix becomes
`[pkg#task]` so identically-named siblings stay distinguishable; if a
member has no `name` field the folder's directory name is used, except
for the workspace root which falls back to the bare task name.
Fixes #27586
