docs : update speculative decoding parameters after refactor (#22397) (#22539)

docs : update speculative decoding parameters after refactor (#22397) (#22539)

* docs : update speculative decoding parameters after refactor (#22397)

Update docs/speculative.md to reflect the new parameter naming scheme
introduced in PR #22397:

- Replace --draft-max/--draft-min with --spec-draft-n-max/--spec-draft-n-min
- Replace --spec-ngram-size-n/m with per-implementation variants
- Add documentation for all new --spec-ngram-*- parameters
- Update all example commands

Assisted-by: llama.cpp:local pi
* pi : add rule to use gh CLI for GitHub resources

Assisted-by: llama.cpp:local pi
* docs : run llama-gen-docs

* arg : fix typo