Models: detect bare Ollama URLs as online

_ping_endpoint() is the reachability fallback the model-endpoint POST
handler invokes when _probe_endpoint() returns no model ids. It GETs
base + "/models" and, on any sub-500 response, returns immediately with
`reachable = (status < 400)`. That early return runs before the
Ollama-native /api/version / /api/tags fallback below it.

For an Ollama URL without /v1 (the quickstart accepts both
http://localhost:11434 and http://127.0.0.1:11434, and the reporter
on #1025 explicitly tried both), the OpenAI-style probe target is
http://127.0.0.1:11434/models. Ollama returns 404 there because /models
only lives under /v1. _ping_endpoint then returned reachable=False and
the picker showed "Added (offline — will retry on next load)" on an
install that was running fine. /api/version was never tried.

Same shape for http://127.0.0.1:11434/api (the native Ollama root):
/api/models is also 404, same premature offline verdict.

_probe_endpoint() does fall through to /api/tags on a 4xx (the response
raises via raise_for_status), so the endpoint quietly recovers once
cached_models becomes non-empty on the next background refresh —
matching the second commenter's "had to disconnect manually then
reconnect for it to be detected" note. The bug is most visible while
no models are pulled yet (cached_models stays empty, _ping_endpoint
keeps voting offline).

Fix:

- Hoist the Ollama-shaped-URL test (port == 11434 or "ollama" in
  hostname — the same condition _probe_endpoint already uses) to the
  top of the function so both code paths share it.
- Stop short-circuiting on 4xx when the URL looks like Ollama: fall
  through to the existing /api/version + /api/tags reachability loop
  so an alive Ollama gets recognised even when its OpenAI surface has
  the wrong prefix for the user's input.
- Fix the `root` computation in that loop to strip a trailing /api as
  well as /v1, so http://127.0.0.1:11434/api no longer gets probed at
  /api/api/version.
- 4xx on non-Ollama hosts keeps the current semantics: a 401 from
  api.openai.com/v1/models is still a definitive offline verdict, not
  a reason to GET /api/version on OpenAI.

Closes #1025.

routes/model_routes.py

@@ -348,7 +348,24 @@ def _ping_endpoint(base_url: str, api_key: str = None, timeout: float = 1.5) ->
     if api_key:
         headers["Authorization"] = f"Bearer {api_key}"
 
+    # Ollama exposes /v1/models (OpenAI-compatible) AND native /api/version,
+    # /api/tags. The OpenAI-style GET base + "/models" returns 404 when the
+    # base is the host root or the native /api root (e.g. http://localhost:11434,
+    # http://localhost:11434/api) because /models lives under /v1 there. Treat
+    # 4xx on a port-11434 / Ollama-named base as "try the native paths" rather
+    # than as a definitive offline verdict — Ollama is reachable, it just
+    # doesn't speak OpenAI on that prefix. Without this gate the quickstart
+    # marks an alive Ollama as offline whenever cached_models is empty (issue
+    # #1025): _probe_endpoint() falls through to /api/tags on the same 404, but
+    # _ping_endpoint() was returning before that fallback could run.
+    parsed_base = urlparse(base)
+    looks_like_ollama = (
+        parsed_base.port == 11434
+        or "ollama" in (parsed_base.hostname or "").lower()
+    )
+
     url = base + "/models"
+    last_error: Optional[str] = None
     try:
         r = httpx.get(url, headers=headers, timeout=timeout)
         if 300 <= r.status_code < 400:
@@ -360,17 +377,21 @@ def _ping_endpoint(base_url: str, api_key: str = None, timeout: float = 1.5) ->
                     "error": "That is Odysseus, not a model server. Use the Ollama URL, usually http://host.docker.internal:11434/v1 in Docker.",
                 }
             return {"reachable": False, "status_code": r.status_code, "error": f"HTTP {r.status_code} redirect"}
-        if r.status_code < 500:
-            return {"reachable": r.status_code < 400, "status_code": r.status_code, "error": None if r.status_code < 400 else f"HTTP {r.status_code}"}
+        if r.status_code < 400:
+            return {"reachable": True, "status_code": r.status_code, "error": None}
+        if r.status_code < 500 and not looks_like_ollama:
+            return {"reachable": False, "status_code": r.status_code, "error": f"HTTP {r.status_code}"}
+        last_error = f"HTTP {r.status_code}"
     except Exception as e:
         last_error = str(e)[:120]
-    else:
-        last_error = f"HTTP {r.status_code}"
 
     try:
-        parsed = urlparse(base)
-        if parsed.port == 11434 or "ollama" in (parsed.hostname or "").lower():
-            root = base[:-3].rstrip("/") if base.endswith("/v1") else base
+        if looks_like_ollama:
+            root = base
+            for suffix in ("/v1", "/api"):
+                if root.endswith(suffix):
+                    root = root[: -len(suffix)].rstrip("/")
+                    break
             for path in ("/api/version", "/api/tags"):
                 try:
                     r = httpx.get(root + path, timeout=timeout)