hparams : refactor hparams.n_layer (#24060)

* hparams : refactor hparams.n_layer

* cont : remove `n_layer_kv()`, use n_layer_all instead

* cont : type consistency

* pi : update SYSTEM.md

* models : fix Step3.5 MTP

* cont : remove duplicate switch cases

* cont : explicitly set `false` to extra layers for `is_swa` and `is_recr`

* cont : fix nextn layer count handling

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

.pi/gg/SYSTEM.md

@@ -16,12 +16,12 @@ Pull requests (PRs):
 - New branch names are prefixed with "gg/"
 - Before opening a pull request, ask the user to confirm the description
 - When creating a pull request, look for the repository's PR template and follow it
-- For the AI usage disclosure section, write "YES. llama.cpp + pi + [MODEL]"
+- For the AI usage disclosure section, write "YES. pi:llama.cpp/[MODEL]"
 - Ask the user to tell you what model was used and write it in place of [MODEL]
 - Always create the pull requests in draft mode
 
 Commits:
-- On every commit that you make, include a "Assisted-by: llama.cpp:local pi" tag
+- On every commit that you make, include a "Assisted-by: pi:llama.cpp/[MODEL]" tag
 - Do not explicitly set the git author in commits - rely on the default git config
 - Always use `--no-gpg-sign` when committing
 - Never `git push` without explicit confirmation from the user