fix(store,agent): lock WAL sidecars; report real turn ceiling on finalize (#254)

Two self-review findings from #250:

- store/sqlite: os.Chmod only locked the main state.db to 0600; in WAL mode the
  -wal/-shm sidecars hold committed page data (the same diffs/transcripts) and
  inherited the umask default. Chmod them 0600 too, right after the schema write
  materializes them (defense-in-depth atop the 0700 dir). Test asserts sidecar
  perms when present.
- engine/agent: the forced-finalization fall-through error still reported
  maxTurns after the loop bound was raised to maxTurns+maxEmptyRounds; report the
  real ceiling in all three backends.

Author: vanducng

internal/engine/agent/agent.go

@@ -269,7 +269,7 @@ func (a *anthropicAgent) Review(ctx stdctx.Context, rc Context) (engine.ReviewOu
 		emptyRounds = 0
 		params.Messages = append(params.Messages, anthropic.NewUserMessage(toolResults...))
 	}
-	return engine.ReviewOutput{}, fmt.Errorf("agent: forced finalization produced no parseable findings after %d turns", maxTurns)
+	return engine.ReviewOutput{}, fmt.Errorf("agent: forced finalization produced no parseable findings after %d turns", maxTurns+maxEmptyRounds)
 }
 
 // RepairPatch issues one tools-less, code-only completion (system =

internal/engine/agent/codex.go

@@ -273,7 +273,7 @@ func (a *codexAgent) Review(ctx stdctx.Context, rc Context) (engine.ReviewOutput
 		emptyRounds = 0
 		input = append(input, toolItems...)
 	}
-	return engine.ReviewOutput{}, fmt.Errorf("agent: forced finalization produced no parseable findings after %d turns", maxTurns)
+	return engine.ReviewOutput{}, fmt.Errorf("agent: forced finalization produced no parseable findings after %d turns", maxTurns+maxEmptyRounds)
 }
 
 // dispatch runs every function_call in resp, returning function_call_output

internal/engine/agent/openai.go

@@ -250,5 +250,5 @@ func (a *openaiAgent) Review(ctx stdctx.Context, rc Context) (engine.ReviewOutpu
 			params.Messages = append(params.Messages, openai.ToolMessage(out, tc.ID))
 		}
 	}
-	return engine.ReviewOutput{}, fmt.Errorf("agent: forced finalization produced no parseable findings after %d turns", maxTurns)
+	return engine.ReviewOutput{}, fmt.Errorf("agent: forced finalization produced no parseable findings after %d turns", maxTurns+maxEmptyRounds)
 }

internal/store/sqlite/sqlite.go

@@ -91,11 +91,14 @@ func Open(path string) (*Store, error) {
 		_ = db.Close()
 		return nil, fmt.Errorf("migrate schema: %w", err)
 	}
-	// SchemaSQL is the first write, so the DB file is now guaranteed to exist
-	// (WAL mode may not materialize it on Ping alone). Lock it to owner-only —
-	// defense-in-depth atop the 0700 dir — so the persisted diffs/transcripts
-	// aren't world-readable.
+	// SchemaSQL is the first write, so the DB file — and, in WAL mode, its -wal/-shm
+	// sidecars (which also hold committed page data) — now exist. Lock them all to
+	// owner-only, defense-in-depth atop the 0700 dir, so the persisted
+	// diffs/transcripts aren't world-readable. Sidecars may be absent on some paths,
+	// so ignore errors.
 	_ = os.Chmod(path, 0o600)
+	_ = os.Chmod(path+"-wal", 0o600)
+	_ = os.Chmod(path+"-shm", 0o600)
 	if err := migrateReviewColumns(db); err != nil {
 		_ = db.Close()
 		return nil, fmt.Errorf("migrate reviews columns: %w", err)

internal/store/sqlite/sqlite_test.go

@@ -69,6 +69,17 @@ func TestOpenLocksDownPermissions(t *testing.T) {
 	if got := fi.Mode().Perm(); got != 0o600 {
 		t.Errorf("state.db mode = %o, want 600 (holds diffs/transcripts)", got)
 	}
+	// WAL -wal/-shm sidecars hold committed page data too; when present they must
+	// be locked down like the main DB (the schema write above materializes them).
+	for _, sidecar := range []string{path + "-wal", path + "-shm"} {
+		si, err := os.Stat(sidecar)
+		if err != nil {
+			continue // may not exist depending on SQLite's WAL state
+		}
+		if got := si.Mode().Perm(); got != 0o600 {
+			t.Errorf("%s mode = %o, want 600 (holds committed page data)", filepath.Base(sidecar), got)
+		}
+	}
 }
 
 func TestSaveGetRoundTrip(t *testing.T) {