cleanup: archive stale scripts and delete orphaned generate_extra_charts

Archives 8 one-off/backfill/research scripts to scripts/archive/:
- compare_svd_exclude_parties.py (diagnostic)
- compute_test_batch.py (test utility)
- fill_mp_votes_parties.py (backfill)
- generate_compass.py (generates to deleted outputs/)
- inspect_axis.py (diagnostic)
- qa_similarity.py (QA script, references deleted thoughts/ledgers/)
- recompute_svd.py (one-off recompute)
- semantic_gravity_examples.py (research)

Deletes:
- generate_extra_charts.py (0 references, generates to deleted outputs/)
- tests/test_qa_similarity.py (test for archived script)

Adds:
- scripts/archive/README.md explaining archive purpose
- docs/plans/2026-05-01-001-scripts-audit-cleanup-plan.md

tests/test_qa_similarity.py

@@ -1,51 +0,0 @@
-import json
-from pathlib import Path
-
-
-def test_qa_similarity_creates_ledger(tmp_path, monkeypatch):
-    # Prepare monkeypatched database.db
-    class DummyDB:
-        def sample_motions(self, sample_size):
-            assert sample_size == 2
-            return [1, 2]
-
-        def get_cached_similarities(self, motion_id, top_k):
-            # return deterministic neighbors
-            return [
-                {"id": motion_id * 10 + i, "score": 1.0 - i * 0.1} for i in range(top_k)
-            ]
-
-    dummy = DummyDB()
-
-    # Monkeypatch the database module to provide .db — use monkeypatch.setitem
-    # so the override is active for this test and auto-reverts after.
-    import types
-
-    fake_db_module = types.SimpleNamespace(db=dummy)
-
-    import sys
-
-    monkeypatch.setitem(sys.modules, "database", fake_db_module)
-
-    # Ensure thoughts/ledgers inside tmp_path
-    base = tmp_path
-    (base / "thoughts" / "ledgers").mkdir(parents=True)
-
-    # Monkeypatch cwd so ledger writes to tmp_path/thoughts
-    monkeypatch.chdir(base)
-
-    from scripts.qa_similarity import main
-
-    summary = main(db_path=":memory:", sample_size=2, top_k=3)
-
-    assert summary["sample_size"] == 2
-    assert summary["top_k"] == 3
-    assert 1 in summary["motions"]
-    assert 2 in summary["motions"]
-
-    ledger_path = Path(summary["ledger_path"])
-    assert ledger_path.exists()
-
-    data = json.loads(ledger_path.read_text(encoding="utf-8"))
-    assert "motions" in data
-    assert len(data["motions"]) == 2