Correct the short-circuit test's comment to match what it actually guards

The comment claimed swapping the cap and scrub back would fail this
test. It does not: the secret sits at the front of a 90KB payload,
nowhere near the cap boundary, so cap-then-scrub still leaves the
whole key intact for the scrub to catch. This test guards the
PREPENDED POSITION of both terminal concerns (moving them away from
the front of the array fails it); the RELATIVE order between them is
guarded only by the boundary-straddle test. Leaving the old comment
in place risked a future engineer reading this test as redundant
coverage and deleting the straddle test, silently reopening the
exploit.

Author: TheGreatAxios

src/agent/posix-tool-plugins.test.ts

@@ -338,8 +338,15 @@ describe("buildCorePosixToolPlugins", () => {
     // wrapped by the unconditional outer plugins in buildCorePosixToolPlugins.
     // This composes the REAL production array from the builder — not a
     // hand-picked middleware order — with a short-circuiting stand-in spliced
-    // in at ripgrepPlugin's own position, so a future reordering of the real
-    // array (e.g. swapping the cap and scrub back) fails this test.
+    // in at ripgrepPlugin's own position, so moving both terminal concerns
+    // away from the front of the real array fails this test.
+    //
+    // This guards their PREPENDED POSITION only, not the RELATIVE order
+    // between the two of them: the secret here sits at the very front of the
+    // payload, nowhere near the cap boundary, so it survives even under the
+    // exploitable cap-then-scrub order. The relative order is guarded solely
+    // by the boundary-straddle test below — do not treat this test as
+    // redundant with it.
     const secretShapedContent = `AKIAABCDEFGHIJKLMNOP\n${"x".repeat(90_000)}`;
     const shortCircuitingPlugin: ToolPlugin = {
       middleware: () => async (call: ToolCall): Promise<ToolResult> => ({