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>

tests/test_issue60_linux_fixes.py

@@ -2,11 +2,17 @@
 
 1. The 2.x home screen's placeholder (`Ask anything… "<example>"`, cut
    without its closing quote in a narrow box) is not typed input.
+5. The adapter's queries neither create nor remove anything beside
+   opencode's database (a read-write open checkpoints the WAL and deletes
+   the sidecars on close; a plain mode=ro open creates missing ones).
 """
 
 from __future__ import annotations
 
+import os
 import re
+import shutil
+import sqlite3
 import sys
 from pathlib import Path
 
@@ -19,6 +25,7 @@ if str(SKILLS) not in sys.path:
     sys.path.insert(0, str(SKILLS))
 
 from lib_py import stall_watch  # noqa: E402
+from lib_py.agents.base import DiscoveryContext  # noqa: E402
 from lib_py.agents.input_region import extract_input_region  # noqa: E402
 from lib_py.agents.registry import get_adapter  # noqa: E402
 
@@ -80,3 +87,81 @@ def test_stall_watch_sees_the_2x_home_box_empty(name, monkeypatch):
 def test_other_adapters_have_no_placeholder_pattern():
     for agent in ("claude", "agy", "grok", "codex", "hermes"):
         assert get_adapter(agent).input_placeholder_pattern is None, agent
+
+
+# ---------------------------------------------------------------------------
+# 5. the queries leave the files beside the database alone
+# ---------------------------------------------------------------------------
+V2_DDL = ("CREATE TABLE session_v2 (id TEXT PRIMARY KEY, parent_id TEXT, directory TEXT NOT NULL, time_created INTEGER NOT NULL)",
+          "CREATE TABLE session_message (id TEXT PRIMARY KEY, session_id TEXT)")
+
+QUERIES = {
+    "verify_artifact": (lambda a, ctx, db: a.verify_artifact("ses_main", ctx), True),
+    "discover": (lambda a, ctx, db: a.discover(ctx), ["ses_main"]),
+    "_has_session": (lambda a, ctx, db: a._has_session(db, "ses_main"), True),
+    "_descendants": (lambda a, ctx, db: a._descendants(db, "ses_main"), ["ses_child"]),
+    "residual_artifacts": (lambda a, ctx, db: any("session_v2.id: 1 rows" in r
+                                                  for r in a.residual_artifacts("ses_main", ctx)), True),
+}
+
+
+def _wal_writer(db: Path, ws: Path) -> sqlite3.Connection:
+    """An open WAL connection holding the schema and two sessions: until it
+    closes, the rows live in the -wal only."""
+    conn = sqlite3.connect(str(db))
+    conn.execute("PRAGMA journal_mode=wal")
+    for stmt in V2_DDL:
+        conn.execute(stmt)
+    conn.execute("INSERT INTO session_v2 VALUES ('ses_main', NULL, ?, 2000000)", (str(ws),))
+    conn.execute("INSERT INTO session_v2 VALUES ('ses_child', 'ses_main', ?, 3000000)", (str(ws),))
+    conn.execute("INSERT INTO session_message VALUES ('msg-1', 'ses_main')")
+    conn.commit()
+    return conn
+
+
+@pytest.fixture
+def wal_home(tmp_path, monkeypatch):
+    """(adapter, ctx, db, ws, make(state)) - make builds the database in one
+    of three states: `clean` (closed: no sidecars), `leftover` (both sidecars
+    left behind by a writer that is gone, the rows only in the -wal),
+    `writer` (a live writer whose rows are only in the -wal)."""
+    home, ws = tmp_path / "home", tmp_path / "ws"
+    ws.mkdir()
+    db = home / ".local" / "share" / "opencode" / "opencode.db"
+    db.parent.mkdir(parents=True)
+    adapter = get_adapter("opencode")
+    monkeypatch.setattr(adapter, "_bin", lambda ctx: None)  # the default path, no subprocess
+    ctx = DiscoveryContext(workspace=str(ws), agent_name="opencode", home_dir=str(home))
+    opened = []
+
+    def make(state):
+        if state == "clean":
+            _wal_writer(db, ws).close()
+        elif state == "leftover":
+            src = tmp_path / "src" / "opencode.db"
+            src.parent.mkdir()
+            conn = _wal_writer(src, ws)
+            for suffix in ("", "-wal", "-shm"):
+                shutil.copyfile(str(src) + suffix, str(db) + suffix)
+            conn.close()
+        else:
+            opened.append(_wal_writer(db, ws))
+        return sorted(os.listdir(db.parent))
+
+    yield adapter, ctx, str(db), ws, make
+    for conn in opened:
+        conn.close()
+
+
+@pytest.mark.parametrize("query", sorted(QUERIES))
+@pytest.mark.parametrize("state,listing", [
+    ("clean", ["opencode.db"]),
+    ("leftover", ["opencode.db", "opencode.db-shm", "opencode.db-wal"]),
+    ("writer", ["opencode.db", "opencode.db-shm", "opencode.db-wal"]),
+])
+def test_a_query_reads_right_and_leaves_the_sidecars_alone(wal_home, state, listing, query):
+    adapter, ctx, db, ws, make = wal_home
+    assert make(state) == listing
+    run, expected = QUERIES[query]
+    assert run(adapter, ctx, db) == expected
+    assert sorted(os.listdir(os.path.dirname(db))) == listing