fix(lib): jsonl-store's docstring stops lying; mode option added; lib bypasses adopted

The header claimed 'single source of truth... the ONLY copy' with write-time
injection REJECTION — while appendJsonl never screened anything, only 1 of
~10 JSONL stores imported it, and a bypass appender lived in the same
directory. Now: the contract is explicit (screening is the CALLER's job via
hasInjection/firstInjectionMatch; the enforcing callers are named), a
option applies 0600 at create for sensitive stores, and the lib bypasses are
adopted (gstack-memory-helpers ×2, redact-audit-log — which keeps its chmod
backstop for files created looser by pre-mode versions). browse/src keeps
its own appenders by design (compiled-binary surface, own secure-append
helper) and the header now says so. gstack-decision's batched archive append
stays deliberate (single-write crash-window semantics appendJsonl's
one-record contract can't express).

New pins: 0600-at-create, and a test that documents appendJsonl does NOT
self-screen — so nobody can re-document it as self-screening without making
it true.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/redact-audit-log.ts

@@ -18,6 +18,7 @@ import * as fs from "fs";
 import * as os from "os";
 import * as path from "path";
 import { createHash } from "crypto";
+import { appendJsonl } from "./jsonl-store";
 
 export interface SemanticReviewEntry {
   ts: string;
@@ -43,7 +44,9 @@ export function appendSemanticReview(entry: SemanticReviewEntry): void {
     const dir = securityDir();
     fs.mkdirSync(dir, { recursive: true });
     const file = path.join(dir, "semantic-reviews.jsonl");
-    fs.appendFileSync(file, JSON.stringify(entry) + "\n");
+    // 0600 at create via appendJsonl's mode opt; the chmod backstop covers
+    // files created looser by pre-mode versions.
+    appendJsonl(file, entry, { mode: 0o600 });
     try {
       fs.chmodSync(file, 0o600);
     } catch {