Add name suggestion engine with API endpoint and tests

Expand services/naming.py with suggest_names() that picks random words
from a category while excluding nicknames already used in the run. Add
GET /runs/{run_id}/name-suggestions?count=10 endpoint that reads the
run's naming_scheme and returns filtered suggestions. Includes 12 unit
tests covering selection, exclusion, exhaustion, and cross-category
independence.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/app/services/naming.py

@@ -1,4 +1,5 @@
 import json
+import random
 from functools import lru_cache
 from pathlib import Path
 
@@ -16,3 +17,29 @@ def _load_dictionary() -> dict[str, list[str]]:
 def get_naming_categories() -> list[str]:
     """Return sorted list of available naming category names."""
     return sorted(_load_dictionary().keys())
+
+
+def get_words_for_category(category: str) -> list[str]:
+    """Return the word list for a category, or empty list if not found."""
+    return _load_dictionary().get(category, [])
+
+
+def suggest_names(
+    category: str,
+    used_names: set[str],
+    count: int = 10,
+) -> list[str]:
+    """Pick random name suggestions from a category, excluding used names.
+
+    Returns up to `count` names. If the category is nearly exhausted,
+    returns fewer.
+    """
+    words = get_words_for_category(category)
+    if not words:
+        return []
+
+    available = [w for w in words if w not in used_names]
+    if not available:
+        return []
+
+    return random.sample(available, min(count, len(available)))