fix: Cookbook local GGUF serving inside Docker (#1264)

* fix: Cookbook local GGUF serving inside Docker

Cookbook’s in-container GGUF serve flow had multiple Docker-specific breakages that made local llama.cpp models fail or register against the wrong endpoint.

Fixes included here:

use the scanned model cache root when generating GGUF serve commands instead of hardcoding $HOME/.cache/huggingface/hub
fix malformed llama.cpp preflight build lines that generated invalid bash in serve runner scripts
preserve loopback model URLs inside Docker when the target port is already reachable from the Odysseus container, instead of rewriting them unconditionally to host.docker.internal
Before this change, Docker local serves could fail in several ways:

Cookbook pointed llama.cpp at the wrong GGUF path
generated serve runner scripts crashed before launch with a shell syntax error
successfully started in-container model servers were auto-registered as host.docker.internal: instead of localhost/127.0.0.1
This makes the Docker Cookbook path work as expected for: downloaded GGUF -> local llama.cpp serve -> endpoint registration

* test: add test for docker-local endpoint rewrites

routes/model_routes.py

@@ -148,6 +148,32 @@ def _docker_host_gateway_reachable() -> bool:
     except OSError:
         return False
 
+def _container_loopback_reachable(base_url: str, timeout: float = 0.2) -> bool:
+    """True when the requested loopback host:port is already reachable from
+    inside the current container.
+
+    This distinguishes "a model server running alongside Odysseus in the same
+    container" from "a model server running on the Docker host". Only the
+    latter should be rewritten to host.docker.internal.
+    """
+    try:
+        parsed = urlparse(base_url)
+    except Exception:
+        return False
+    host = (parsed.hostname or "").lower()
+    port = parsed.port
+    if host not in _LOOPBACK_HOSTS or not port:
+        return False
+    probe_host = "::1" if host == "::1" else "127.0.0.1"
+    family = socket.AF_INET6 if probe_host == "::1" else socket.AF_INET
+    try:
+        with socket.socket(family, socket.SOCK_STREAM) as sock:
+            sock.settimeout(timeout)
+            sock.connect((probe_host, port))
+        return True
+    except OSError:
+        return False
+
 
 def _rewrite_loopback_for_docker(base_url: str, *, container_local: bool = False) -> str:
     """Rewrite a loopback model-endpoint URL to ``host.docker.internal`` when
@@ -176,6 +202,8 @@ def _rewrite_loopback_for_docker(base_url: str, *, container_local: bool = False
     if host in _ANY_BIND_HOSTS and not _docker_host_gateway_reachable():
         netloc = "127.0.0.1" + (f":{parsed.port}" if parsed.port else "")
         return urlunparse(parsed._replace(netloc=netloc))
+    if _container_loopback_reachable(base_url):
+        return base_url
     if not _docker_host_gateway_reachable():
         return base_url
     netloc = "host.docker.internal" + (f":{parsed.port}" if parsed.port else "")