feat: model compatibility warning on HF lookup

- GET /api/models/lookup now returns compatible: bool and warning: str|null
- compatible=false + warning when pipeline_tag is absent (no task tag on HF)
  or present but not in the supported adapter map
- Warning message names the unsupported pipeline_tag and lists supported types
- ModelsView: yellow compat-warning banner below preview description;
  Add button relabels to "Add anyway" with muted styling when incompatible
- test_models: accept 405 for path-traversal DELETE tests (StaticFiles mount
  returns 405 for non-GET methods when web/dist exists)

app/models.py

@@ -200,8 +200,26 @@ def lookup_model(repo_id: str) -> dict:
     data = resp.json()
     pipeline_tag = data.get("pipeline_tag")
     adapter_recommendation = _TAG_TO_ADAPTER.get(pipeline_tag) if pipeline_tag else None
-    if pipeline_tag and adapter_recommendation is None:
-        logger.warning("Unknown pipeline_tag %r for %s — no adapter recommendation", pipeline_tag, repo_id)
+
+    # Determine compatibility and surface a human-readable warning
+    _supported = ", ".join(sorted(_TAG_TO_ADAPTER.keys()))
+    if adapter_recommendation is not None:
+        compatible = True
+        warning: str | None = None
+    elif pipeline_tag is None:
+        compatible = False
+        warning = (
+            "This model has no task tag on HuggingFace — adapter type is unknown. "
+            "It may not work with Avocet's email classification pipeline."
+        )
+        logger.warning("No pipeline_tag for %s — no adapter recommendation", repo_id)
+    else:
+        compatible = False
+        warning = (
+            f"\"{pipeline_tag}\" models are not supported by Avocet's email classification adapters. "
+            f"Supported task types: {_supported}."
+        )
+        logger.warning("Unsupported pipeline_tag %r for %s", pipeline_tag, repo_id)
 
     # Estimate model size from siblings list
     siblings = data.get("siblings") or []
@@ -216,6 +234,8 @@ def lookup_model(repo_id: str) -> dict:
         "repo_id": repo_id,
         "pipeline_tag": pipeline_tag,
         "adapter_recommendation": adapter_recommendation,
+        "compatible": compatible,
+        "warning": warning,
         "model_size_bytes": model_size_bytes,
         "description": description,
         "tags": data.get("tags") or [],

tests/test_models.py

@@ -371,15 +371,18 @@ def test_delete_installed_not_found_returns_404(client):
 
 
 def test_delete_installed_path_traversal_blocked(client):
-    """DELETE /installed/../../etc must be blocked (400 or 422)."""
+    """DELETE /installed/../../etc must be blocked.
+    Path traversal normalises to a different URL (/api/etc); if web/dist exists
+    the StaticFiles mount intercepts it and returns 405 (GET/HEAD only).
+    """
     r = client.delete("/api/models/installed/../../etc")
-    assert r.status_code in (400, 404, 422)
+    assert r.status_code in (400, 404, 405, 422)
 
 
 def test_delete_installed_dotdot_name_blocked(client):
     """A name containing '..' in any form must be rejected."""
     r = client.delete("/api/models/installed/..%2F..%2Fetc")
-    assert r.status_code in (400, 404, 422)
+    assert r.status_code in (400, 404, 405, 422)
 
 
 def test_delete_installed_name_with_slash_blocked(client):

web/src/views/ModelsView.vue

@@ -54,12 +54,18 @@
           {{ lookupResult.description }}
         </p>
 
+        <div v-if="lookupResult.warning" class="compat-warning" role="alert">
+          <span class="compat-warning-icon">⚠️</span>
+          <span>{{ lookupResult.warning }}</span>
+        </div>
+
         <button
           class="btn-primary btn-add-queue"
+          :class="{ 'btn-add-queue-warn': !lookupResult.compatible }"
           :disabled="lookupResult.already_installed || lookupResult.already_queued || addingToQueue"
           @click="addToQueue"
         >
-          {{ addingToQueue ? 'Adding…' : 'Add to queue' }}
+          {{ addingToQueue ? 'Adding…' : lookupResult.compatible ? 'Add to queue' : 'Add anyway' }}
         </button>
       </div>
     </section>
@@ -188,6 +194,8 @@ interface LookupResult {
   repo_id: string
   pipeline_tag: string | null
   adapter_recommendation: string | null
+  compatible: boolean
+  warning: string | null
   size: number | null
   description: string | null
   already_installed: boolean
@@ -565,10 +573,34 @@ onUnmounted(() => {
   overflow: hidden;
 }
 
+.compat-warning {
+  display: flex;
+  align-items: flex-start;
+  gap: 0.5rem;
+  padding: 0.6rem 0.75rem;
+  border-radius: var(--radius-sm, 0.25rem);
+  background: color-mix(in srgb, var(--color-warning, #f59e0b) 12%, transparent);
+  border: 1px solid color-mix(in srgb, var(--color-warning, #f59e0b) 40%, transparent);
+  font-size: 0.82rem;
+  color: var(--color-text, #1a2338);
+  line-height: 1.45;
+}
+
+.compat-warning-icon {
+  flex-shrink: 0;
+  line-height: 1.45;
+}
+
 .btn-add-queue {
   align-self: flex-start;
 }
 
+.btn-add-queue-warn {
+  background: var(--color-surface-raised, #e4ebf5);
+  color: var(--color-text-secondary, #6b7a99);
+  border: 1px solid var(--color-border, #d0d7e8);
+}
+
 /* ── Model cards (queue + downloads) ── */
 .model-card {
   border: 1px solid var(--color-border, #a8b8d0);