Fix rowid pk and last_rowid regressions in insert/upsert

Two behaviour regressions in the 4.0 insert/upsert rewrite broke callers
(notably Datasette's write API) that operate on tables without an explicit
primary key. Both are fixed here with regression tests.

1. rowid (and its aliases _rowid_/oid) were rejected as a primary key.
   Table.pks already reports ["rowid"] for a rowid table, but the new pk
   validation raised InvalidColumns because rowid is not listed among the
   table's columns, and the insert success path then raised KeyError when
   looking up the pk value. rowid aliases are now accepted for rowid tables
   and resolve directly to the rowid.

2. An ignored insert (INSERT OR IGNORE that matched an existing row) no
   longer populated last_rowid, and only set last_pk when an explicit pk=
   was passed. It now locates the existing conflicting row by its primary
   key values and reports that row's rowid and pk, rather than relying on
   the connection's last inserted rowid.

Add a shared ROWID_ALIASES constant for the rowid alias names.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E7af8SxFZqiCerJB6MqKnY

tests/test_create.py

@@ -990,6 +990,39 @@ def test_insert_ignore(fresh_db):
     assert rows == [{"id": 1, "bar": 2}]
 
 
+def test_insert_ignore_reports_existing_row(fresh_db):
+    # An ignored insert (row already exists) should point last_rowid and
+    # last_pk at the existing conflicting row - see the Datasette insert API
+    fresh_db["docs"].insert({"id": 1, "title": "Exists"}, pk="id")
+    # Insert a conflicting row with ignore=True and no explicit pk=
+    table = fresh_db["docs"].insert({"id": 1, "title": "One"}, ignore=True)
+    assert table.last_rowid == 1
+    assert table.last_pk == 1
+    assert list(
+        fresh_db["docs"].rows_where("rowid = ?", [table.last_rowid])
+    ) == [{"id": 1, "title": "Exists"}]
+
+
+@pytest.mark.parametrize("rowid_alias", ("rowid", "_rowid_", "oid"))
+@pytest.mark.parametrize("method", ("upsert", "insert_replace", "insert_ignore"))
+def test_pk_rowid_alias_on_rowid_table(fresh_db, rowid_alias, method):
+    # rowid and its aliases are valid primary keys for a rowid table even
+    # though they are not listed among the table's columns - see the Datasette
+    # upsert API against tables without an explicit primary key
+    fresh_db["t"].insert({"title": "Hello"})
+    assert fresh_db["t"].pks == ["rowid"]
+    record = {rowid_alias: 1, "title": "Updated"}
+    if method == "upsert":
+        table = fresh_db["t"].upsert(record, pk=rowid_alias)
+    elif method == "insert_replace":
+        table = fresh_db["t"].insert(record, pk=rowid_alias, replace=True)
+    else:
+        table = fresh_db["t"].insert(record, pk=rowid_alias, ignore=True)
+    assert table.last_pk == 1
+    expected_title = "Hello" if method == "insert_ignore" else "Updated"
+    assert list(fresh_db["t"].rows) == [{"title": expected_title}]
+
+
 def test_insert_ignore_with_pk_after_other_table_insert(fresh_db):
     # https://github.com/simonw/sqlite-utils/issues/554
     user = {"id": "abc", "name": "david"}