fix(metadata): keep the saved trigger-word order on refresh

`civitai.trainedWords` is an ordered array, and the order is what gets
pasted into a prompt: "Copy Trigger Words" and the insert-into-node
action join it as-is. The refresh merge unioned the stored words with the
freshly fetched ones via `list(set(...))`, so any metadata refresh
silently shuffled a user's ordering into an arbitrary one. Now that the
UI exposes reordering, that would look like the feature losing the change
at random.

Merge in order instead: stored words first (in their saved order), then
newly discovered ones, duplicates dropped. `_merge_ordered_unique` keeps
the behaviour easy to assert, and the existing merge test keeps passing
because it compares the result as a set.

py/services/metadata_sync_service.py

@@ -19,6 +19,28 @@ from .model_sources import has_external_source
 logger = logging.getLogger(__name__)
 
 
+def _merge_ordered_unique(existing: Iterable[str], new: Iterable[str]) -> list[str]:
+    """Concatenate two word lists, dropping duplicates without reordering.
+
+    Trigger word order is meaningful: the sequence stored in
+    ``civitai.trainedWords`` is the order used when building prompts, and users
+    can reorder it in the UI. A plain ``set`` union used to shuffle that order on
+    every metadata refresh, so existing words are kept first (in their saved
+    order) and newly discovered ones are appended.
+    """
+
+    merged: list[str] = []
+    seen: set[str] = set()
+
+    for word in list(existing) + list(new):
+        if word in seen:
+            continue
+        seen.add(word)
+        merged.append(word)
+
+    return merged
+
+
 class MetadataProviderProtocol(Protocol):
     """Subset of metadata provider interface consumed by the sync service."""
 
@@ -115,9 +137,10 @@ class MetadataSyncService:
                 )
 
             if "trainedWords" in existing_civitai:
-                existing_trained = existing_civitai.get("trainedWords", [])
+                existing_trained = existing_civitai.get("trainedWords", []) or []
-                new_trained = civitai_metadata.get("trainedWords", [])
+                new_trained = civitai_metadata.get("trainedWords", []) or []
-                merged_trained = list(set(existing_trained + new_trained))
+                # Order preserving merge: the saved order drives prompt order.
+                merged_trained = _merge_ordered_unique(existing_trained, new_trained)
                 merged_civitai["trainedWords"] = merged_trained
 
             local_metadata["civitai"] = merged_civitai

tests/services/test_metadata_sync_service.py

@@ -6,7 +6,7 @@ import pytest
 
 from py.services.connectivity_guard import OFFLINE_COOLDOWN_ERROR, OFFLINE_FRIENDLY_MESSAGE
 from py.services.errors import RateLimitError
-from py.services.metadata_sync_service import MetadataSyncService
+from py.services.metadata_sync_service import MetadataSyncService, _merge_ordered_unique
 
 
 class DummySettings:
@@ -112,6 +112,49 @@ async def test_update_model_metadata_merges_and_persists():
     )
 
 
+def test_merge_ordered_unique_keeps_first_seen_order():
+    assert _merge_ordered_unique(["b", "a"], ["a", "c", "b", "d"]) == [
+        "b",
+        "a",
+        "c",
+        "d",
+    ]
+    assert _merge_ordered_unique([], ["x"]) == ["x"]
+    assert _merge_ordered_unique(["x"], []) == ["x"]
+
+
+@pytest.mark.asyncio
+async def test_update_model_metadata_preserves_trained_word_order():
+    """Trigger word order (prompt order) must survive a metadata refresh."""
+
+    helpers = build_service()
+
+    local = {
+        "civitai": {"trainedWords": ["zeta style", "alpha", "beta"]},
+        "model_name": "Local",
+    }
+    remote = {
+        "source": "api",
+        "trainedWords": ["beta", "gamma", "alpha"],
+        "model": {"name": "Remote Model"},
+    }
+
+    result = await helpers.service.update_model_metadata(
+        "path/to/model.metadata.json",
+        local,
+        remote,
+        helpers.default_provider,
+    )
+
+    # Saved order first, newly discovered words appended, duplicates dropped
+    assert result["civitai"]["trainedWords"] == [
+        "zeta style",
+        "alpha",
+        "beta",
+        "gamma",
+    ]
+
+
 @pytest.mark.asyncio
 async def test_update_model_metadata_propagates_civitai_autov3():
     helpers = build_service()