fix: isolate per-adapter search failures in the pipeline match loop

Wrap each adapter's search() call in the match stage in try/except so
a down source (dead slskd, Qobuz auth error, etc.) contributes no
candidates instead of crashing run_pipeline and killing the worker.

worker/lyra_worker/pipeline.py

@@ -126,7 +126,12 @@ def run_pipeline(
     _set_state(conn, job_id, "matching", "match")
     found: list[Candidate] = []
     for adapter in adapters:
-        for c in adapter.search(target):
+        try:
+            results = adapter.search(target)
+        except Exception as e:  # a down source contributes no candidates, never crashes the job
+            print(f"pipeline: adapter {adapter.name} search failed: {e}", flush=True)
+            continue
+        for c in results:
             found.append(replace(c, source_tier=adapter.tier, confidence=score_confidence(target, c)))
     _persist_candidates(conn, job_id, found)
 

worker/tests/test_pipeline_hardening.py

@@ -0,0 +1,35 @@
+from lyra_worker.adapters.youtube import YouTubeAdapter
+from lyra_worker.claim import claim_next
+from lyra_worker.pipeline import run_pipeline
+from tests.conftest import insert_request
+from tests.test_youtube_adapter import FakeYtClient
+
+
+class ExplodingAdapter:
+    name = "boom"
+    tier = 0
+
+    def health(self):
+        return True
+
+    def search(self, target):
+        raise RuntimeError("search backend down")
+
+    def download(self, candidate, dest, on_progress):
+        raise AssertionError("should never be called")
+
+
+def test_one_failing_source_does_not_crash_the_job(conn):
+    job_id = insert_request(conn, artist="John Mayer", album="Continuum")
+    claim_next(conn)
+    # track_count must be 10 to match FakeYtClient.download's hardcoded return value,
+    # otherwise the pipeline's tag-stage integrity check fails independently of hardening.
+    yt = [{"source_ref": "yt1", "title": "Continuum", "artist": "John Mayer", "track_count": 10}]
+    # The exploding adapter must not abort the pipeline; YouTube should still win.
+    run_pipeline(conn, job_id, [ExplodingAdapter(), YouTubeAdapter(FakeYtClient(results=yt))], dest_root="/tmp/lib")
+
+    with conn.cursor() as cur:
+        cur.execute('SELECT state FROM "Job" WHERE id = %s', (job_id,))
+        assert cur.fetchone()[0] == "imported"
+        cur.execute('SELECT source FROM "Candidate" WHERE "jobId" = %s AND chosen = true', (job_id,))
+        assert cur.fetchone()[0] == "youtube"