fix(opencode): queries open the database read-only without touching its sidecars (Issue #60, Linux item 5)

A read-write open checkpointed the WAL and deleted -wal/-shm on close; a
plain mode=ro open created missing ones and left them. _ro_connect uses the
sidecars only when both exist (a live writer keeps them) and reads the file
as immutable otherwise. verify_artifact, _has_session, discover,
_descendants and residual_artifacts (db_rows_naming takes a connect) use it;
the purge's own writes are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.agents/skills/lib_py/agents/base.py

@@ -108,14 +108,15 @@ def scan_names(root: str, uuid: str, skip=()) -> list:
     return sorted(found)
 
 
-def db_rows_naming(db: str, uuid: str, columns=(), id_tables=()) -> list:
+def db_rows_naming(db: str, uuid: str, columns=(), id_tables=(), connect=None) -> list:
     """"<db> (<table>.<col>: <n> rows)" for every table holding rows of this
     conversation in one of `columns`, or in the id column of an `id_tables`
-    (table, column) pair (Issue #31). Read-only; unreadable tables are skipped."""
+    (table, column) pair (Issue #31). Read-only; unreadable tables are skipped.
+    `connect(db)` opens the database (default: a mode=ro URI)."""
     if not _plausible_id(uuid) or not db or not os.path.isfile(db):
         return []
     try:
-        conn = sqlite3.connect(f"file:{quote(os.path.abspath(db))}?mode=ro", uri=True)
+        conn = connect(db) if connect else sqlite3.connect(f"file:{quote(os.path.abspath(db))}?mode=ro", uri=True)
     except Exception:
         return []
     found = []