feat(enrichers): web_search DuckDuckGo + tests pytest de los 5 enrichers

Anade enricher web_search aplicable a nodos text/Concept/Topic. Hace
POST a html.duckduckgo.com con la query del nodo, parsea resultados
con HTMLParser stdlib, decodifica el redirect uddg= y crea N nodos
Url con relacion SEARCH_RESULT_OF apuntando al nodo origen.

Encadenable: tras web_search, fetch_webpage sobre cada Url completa
el pipeline search -> fetch -> extract.

Defensa contra ops_db_path mal resuelto: normaliza backslashes,
resuelve relativo contra app_dir, valida que la tabla entities
exista antes de tocar nada (exit codes 7/8/9 con JSON resumen).

Tests pytest (16/16 verde): conftest con operations.db temp +
schema minimo, stub de requests via PYTHONPATH para mockear red.
Cubre los 5 enrichers (extract_domain, fetch_webpage, extract_links,
extract_text_entities, web_search) + sanity check de manifests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_web_search.py

@@ -0,0 +1,97 @@
+"""Tests del enricher web_search (DuckDuckGo HTML)."""
+from __future__ import annotations
+
+from pathlib import Path
+
+from conftest import (
+    base_ctx, list_entities, list_relations, make_node, run_enricher,
+    stub_requests, TESTS_DIR,
+)
+
+
+DDG_FIXTURE = TESTS_DIR / "fixtures" / "ddg_results.html"
+
+
+def test_web_search_creates_url_results_for_text_node(
+        ops_db, app_dir, registry_root, tmp_path):
+    make_node(ops_db, node_id="t1", name="tomate",
+              type_ref="text", metadata={})
+    plan = {
+        "match": [
+            {"contains": "duckduckgo.com",
+             "text": DDG_FIXTURE.read_text(encoding="utf-8"),
+             "status": 200},
+        ],
+        "default": {"text": "", "status": 404},
+    }
+    env = stub_requests(tmp_path, plan)
+
+    ctx = base_ctx(ops_db=ops_db, app_dir=app_dir, registry_root=registry_root,
+                   node_id="t1", node_name="tomate", node_type="text",
+                   params={"limit": 5})
+
+    rc, out, err = run_enricher("web_search", ctx, env=env)
+    assert rc == 0, f"stderr={err}"
+    assert out is not None, err
+    assert out["engine"] == "duckduckgo"
+    assert out["results"] == 3, out
+    assert out["entities_added"] == 3
+    assert out["relations_added"] == 3
+
+    urls = list_entities(ops_db, type_ref="Url")
+    targets = {e["metadata"].get("url") for e in urls}
+    assert "https://es.wikipedia.org/wiki/Tomate" in targets
+    assert "https://www.botanical-online.com/alimentos/tomate-propiedades" in targets
+
+    rels = list_relations(ops_db, name="SEARCH_RESULT_OF")
+    assert len(rels) == 3
+    assert all(r["to_entity"] == "t1" for r in rels)
+
+    # Metadata enriquecida.
+    wiki = next(e for e in urls
+                if e["metadata"].get("url") == "https://es.wikipedia.org/wiki/Tomate")
+    assert wiki["metadata"]["query"] == "tomate"
+    assert wiki["metadata"]["rank"] == 1
+    assert "Wikipedia" in wiki["metadata"]["title"]
+
+
+def test_web_search_uses_metadata_query_over_name(ops_db, app_dir,
+                                                    registry_root, tmp_path):
+    """metadata.query debe ganar prioridad sobre node_name."""
+    make_node(ops_db, node_id="t1", name="placeholder",
+              type_ref="text", metadata={"query": "tomate"})
+    plan = {"match": [{"contains": "duckduckgo.com",
+                       "text": DDG_FIXTURE.read_text(encoding="utf-8")}]}
+    env = stub_requests(tmp_path, plan)
+    ctx = base_ctx(ops_db=ops_db, app_dir=app_dir, registry_root=registry_root,
+                   node_id="t1", node_name="placeholder", node_type="text",
+                   metadata={"query": "tomate"})
+    rc, out, err = run_enricher("web_search", ctx, env=env)
+    assert rc == 0, err
+    assert out["query"] == "tomate"
+
+
+def test_web_search_limit_truncates_results(ops_db, app_dir, registry_root,
+                                              tmp_path):
+    make_node(ops_db, node_id="t1", name="tomate", type_ref="text")
+    plan = {"match": [{"contains": "duckduckgo.com",
+                       "text": DDG_FIXTURE.read_text(encoding="utf-8")}]}
+    env = stub_requests(tmp_path, plan)
+    ctx = base_ctx(ops_db=ops_db, app_dir=app_dir, registry_root=registry_root,
+                   node_id="t1", node_name="tomate", node_type="text",
+                   params={"limit": 1})
+    rc, out, err = run_enricher("web_search", ctx, env=env)
+    assert rc == 0, err
+    assert out["results"] == 1
+    assert out["entities_added"] == 1
+
+
+def test_web_search_no_query_fails_clean(ops_db, app_dir, registry_root,
+                                           tmp_path):
+    make_node(ops_db, node_id="t1", name="", type_ref="text", metadata={})
+    env = stub_requests(tmp_path, {"default": {"text": "", "status": 200}})
+    ctx = base_ctx(ops_db=ops_db, app_dir=app_dir, registry_root=registry_root,
+                   node_id="t1", node_name="", node_type="text")
+    rc, out, err = run_enricher("web_search", ctx, env=env)
+    assert rc == 2
+    assert "sin query" in err