server: add presets (config) when using multiple models (#17859)

* llama-server: recursive GGUF loading

Replace flat directory scan with recursive traversal using
std::filesystem::recursive_directory_iterator. Support for
nested vendor/model layouts (e.g. vendor/model/*.gguf).
Model name now reflects the relative path within --models-dir
instead of just the filename. Aggregate files by parent
directory via std::map before constructing local_model

* server : router config POC (INI-based per-model settings)

* server: address review feedback from @aldehir and @ngxson

PEG parser usage improvements:
- Simplify parser instantiation (remove arena indirection)
- Optimize grammar usage (ws instead of zero_or_more, remove optional wrapping)
- Fix last line without newline bug (+ operator instead of <<)
- Remove redundant end position check

Feature scope:
- Remove auto-reload feature (will be separate PR per @ngxson)
- Keep config.ini auto-creation and template generation
- Preserve per-model customization logic

Co-authored-by: aldehir <aldehir@users.noreply.github.com>
Co-authored-by: ngxson <ngxson@users.noreply.github.com>

* server: adopt aldehir's line-oriented PEG parser

Complete rewrite of INI parser grammar and visitor:
- Use p.chars(), p.negate(), p.any() instead of p.until()
- Support end-of-line comments (key=value # comment)
- Handle EOF without trailing newline correctly
- Strict identifier validation ([a-zA-Z_][a-zA-Z0-9_.-]*)
- Simplified visitor (no pending state, no trim needed)
- Grammar handles whitespace natively via eol rule

Business validation preserved:
- Reject section names starting with LLAMA_ARG_*
- Accept only keys starting with LLAMA_ARG_*
- Require explicit section before key-value pairs

Co-authored-by: aldehir <aldehir@users.noreply.github.com>

* server: fix CLI/env duplication in child processes

Children now receive minimal CLI args (executable, model, port, alias)
instead of inheriting all router args. Global settings pass through
LLAMA_ARG_* environment variables only, eliminating duplicate config
warnings.

Fixes: Router args like -ngl, -fa were passed both via CLI and env,
causing 'will be overwritten' warnings on every child spawn

* add common/preset.cpp

* fix compile

* cont

* allow custom-path models

* add falsey check

* server: fix router model discovery and child process spawning

- Sanitize model names: replace / and \ with _ for display
- Recursive directory scan with relative path storage
- Convert relative paths to absolute when spawning children
- Filter router control args from child processes
- Refresh args after port assignment for correct port value
- Fallback preset lookup for compatibility
- Fix missing argv[0]: store server binary path before base_args parsing

* Revert "server: fix router model discovery and child process spawning"

This reverts commit e3832b42eeea7fcb108995966c7584479f745857.

* clarify about "no-" prefix

* correct render_args() to include binary path

* also remove arg LLAMA_ARG_MODELS_PRESET for child

* add co-author for ini parser code

Co-authored-by: aldehir <hello@alde.dev>

* also set LLAMA_ARG_HOST

* add CHILD_ADDR

* Remove dead code

---------

Co-authored-by: aldehir <aldehir@users.noreply.github.com>
Co-authored-by: ngxson <ngxson@users.noreply.github.com>
Co-authored-by: Xuan Son Nguyen <son@huggingface.co>
Co-authored-by: aldehir <hello@alde.dev>

tools/server/server-models.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "common.h"
+#include "preset.h"
 #include "server-http.h"
 
 #include <mutex>
@@ -47,6 +48,7 @@ static std::string server_model_status_to_string(server_model_status status) {
 }
 
 struct server_model_meta {
+    common_preset preset;
     std::string name;
     std::string path;
     std::string path_mmproj; // only available if in_cache=false
@@ -54,7 +56,7 @@ struct server_model_meta {
     int port = 0;
     server_model_status status = SERVER_MODEL_STATUS_UNLOADED;
     int64_t last_used = 0; // for LRU unloading
-    std::vector<std::string> args; // additional args passed to the model instance (used for debugging)
+    std::vector<std::string> args; // args passed to the model instance, will be populated by render_args()
     int exit_code = 0; // exit code of the model instance process (only valid if status == FAILED)
 
     bool is_active() const {
@@ -66,6 +68,19 @@ struct server_model_meta {
     }
 };
 
+// the server_presets struct holds the presets read from presets.ini
+// as well as base args from the router server
+struct server_presets {
+    common_presets presets;
+    common_params_context ctx_params;
+    std::map<common_arg, std::string> base_args;
+    std::map<std::string, common_arg> control_args; // args reserved for server control
+
+    server_presets(int argc, char ** argv, common_params & base_params, const std::string & models_dir);
+    common_preset get_preset(const std::string & name);
+    void render_args(server_model_meta & meta);
+};
+
 struct subprocess_s;
 
 struct server_models {
@@ -85,14 +100,21 @@ private:
     std::vector<std::string> base_args;
     std::vector<std::string> base_env;
 
+    server_presets presets;
+
     void update_meta(const std::string & name, const server_model_meta & meta);
 
     // unload least recently used models if the limit is reached
     void unload_lru();
 
+    // not thread-safe, caller must hold mutex
+    void add_model(server_model_meta && meta);
+
 public:
     server_models(const common_params & params, int argc, char ** argv, char ** envp);
 
+    void load_models();
+
     // check if a model instance exists
     bool has_model(const std::string & name);
 
@@ -102,8 +124,7 @@ public:
     // return a copy of all model metadata
     std::vector<server_model_meta> get_all_meta();
 
-    // if auto_load is true, load the model with previous args if any
-    void load(const std::string & name, bool auto_load);
+    void load(const std::string & name);
     void unload(const std::string & name);
     void unload_all();