docs: tighten parallel tool-call prose

packages/fs/tool-fs/src/read.ts

@@ -84,12 +84,7 @@ export function applyReadTool(ctx: Context, caps: ReadToolCaps): void {
       offset: { type: 'number', description: '1-based first line to return. Defaults to 1.' },
       limit: { type: 'number', description: `Maximum number of lines to return. Defaults to ${caps.limit}.` },
     },
-    // Read-only. Its one side effect is the synchronous `fs/observed` version
-    // recorder (a WeakMap write; see below and the fs-policy plugin): concurrent
-    // same-target reads race last-writer-wins on that record, which is safe because
-    // it is NOT the safety boundary — write/edit stay exclusive barriers and
-    // re-check the version in-lock, so a stale observation only makes a later edit
-    // fail closed with FS_STALE_VERSION.
+    // Observation races fail closed because guarded mutations re-check the version in-lock.
     isConcurrencySafe: () => true,
     async execute(args, exec): Promise<ContentBlock[]> {
       const input = parseReadArgs(args, caps.limit)