fix: validate set and shopt options when reading a Taskfile

[posidoni]

• I have read and followed the Contribution Guide

Follow-up to #2429. The panic from that issue was fixed upstream in mvdan/sh, but an invalid set:/shopt: option is still only reported when a command actually runs — once per command, with no hint about the actual mistake:

task: [default] echo "hello"
shopt: invalid option name "pipefail"
task: Failed to run task "default": exit status 1

This PR validates set and shopt lists when the Taskfile is read (root, task and command level), following the approach of #2892:

task: invalid shopt option "pipefail" (did you mean to put it in "set"?)
file: Taskfile.yml:1:1

• Valid values mirror the interpreter's unexported posixOptsTable/bashOptsTable (mvdan.cc/sh/v3/interp), i.e. exactly what works at runtime.
• shopt: ["-o", "pipefail"] keeps working: a -o entry switches validation of the remaining entries to set options, matching shopt -s -o semantics (covered by a regression test).
• When an option is placed in the wrong list, the error suggests the right one (pipefail → set, globstar → shopt).
• schema.json: the shopt enum was missing three supported options (dotglob, extglob, nocaseglob) — extended to all six; reference docs updated accordingly.

Note on behavior: an invalid option now fails at parse time even if the task declaring it never runs — consistent with other Taskfile validation such as #2892.

Tested with four new tests (an invalid option at each of the three levels, plus the -o regression) and a full go test ./... run.

Disclosure per the AI usage policy: this PR (code and description) was prepared with AI assistance. I reviewed and tested all changes and can explain every line.

[trulede]

IMHO I think it would be better if errors with options were raised by mvdan (which I think does this already, perhaps?) than to have to keep such a list up to date.

End effect would be (is) the same, an error.