Clamp Pixabay per_page to API-required 3-200 range

Pixabay rejects per_page outside 3-200 with HTTP 400. The stock_sources
adapter already clamped, but the PixabayVideo and PixabayImage tools
passed the value through raw, so callers using per_page < 3 got a 400.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/tools/test_pixabay_per_page_clamp.py

@@ -0,0 +1,62 @@
+"""Pixabay rejects per_page outside 3-200 with HTTP 400, so every
+Pixabay caller must clamp before building the request."""
+
+import requests
+
+from tools.graphics.pixabay_image import PixabayImage
+from tools.video.pixabay_video import PixabayVideo
+from tools.video.stock_sources.base import SearchFilters
+from tools.video.stock_sources.pixabay_video import PixabayVideoSource
+
+
+class _FakeResponse:
+    def raise_for_status(self):
+        pass
+
+    def json(self):
+        return {"hits": [], "total": 0}
+
+
+def _capture_get(captured):
+    def fake_get(url, params=None, timeout=None, **kwargs):
+        captured["params"] = params
+        return _FakeResponse()
+
+    return fake_get
+
+
+def test_pixabay_video_tool_clamps_per_page(monkeypatch):
+    monkeypatch.setenv("PIXABAY_API_KEY", "test-key")
+    captured = {}
+    monkeypatch.setattr(requests, "get", _capture_get(captured))
+
+    PixabayVideo().execute({"query": "sky", "per_page": 1})
+    assert captured["params"]["per_page"] == 3
+
+    PixabayVideo().execute({"query": "sky", "per_page": 500})
+    assert captured["params"]["per_page"] == 200
+
+
+def test_pixabay_image_tool_clamps_per_page(monkeypatch):
+    monkeypatch.setenv("PIXABAY_API_KEY", "test-key")
+    captured = {}
+    monkeypatch.setattr(requests, "get", _capture_get(captured))
+
+    PixabayImage().execute({"query": "sky", "per_page": 1})
+    assert captured["params"]["per_page"] == 3
+
+    PixabayImage().execute({"query": "sky", "per_page": 500})
+    assert captured["params"]["per_page"] == 200
+
+
+def test_pixabay_stock_source_clamps_per_page(monkeypatch):
+    monkeypatch.setenv("PIXABAY_API_KEY", "test-key")
+    captured = {}
+    monkeypatch.setattr(requests, "get", _capture_get(captured))
+
+    source = PixabayVideoSource()
+    source.search("sky", SearchFilters(per_page=1))
+    assert captured["params"]["per_page"] == 3
+
+    source.search("sky", SearchFilters(per_page=500))
+    assert captured["params"]["per_page"] == 200