server: add get_info tool (#26522)

* server: add get_info tool

* fix --rpc in docs

* server: harden get_info probe result handling

Report the OS as unknown when the probe process fails to spawn or times
out, so the diagnostic text from run() is never returned as an OS name.
Strip the probe output on both ends, which also drops the blank line
that ver prints before the version on Windows. Name the output and
timeout limits, and report an unreadable working directory as unknown
instead of an empty string.

* server: simplify get_info result handling

Drop the named limits and the working directory error branch, keeping
the probe result handling to a single expression.

---------

Co-authored-by: Pascal <admin@serveurperso.com>

common/common.h

@@ -739,6 +739,8 @@ struct common_params {
     llama_progress_callback load_progress_callback = NULL;
     void *                  load_progress_callback_user_data = NULL;
     bool no_alloc = false; // Don't allocate model buffers
+
+    bool is_gen_docs = false; // whether we are running inside llama-gen-docs
 };
 
 // call once at the start of a program if it uses libcommon