test(W7c): match redact scan-at-sink exact-bytes rule case-insensitively

W7c conversion (t02 #13). Credential-handling checks (mktemp, --from-file,
exit codes 3/2/0, visibility lookups, no HIGH skip flag) are unchanged.

Removed assertion group (invariant -> remaining protection):
- /EXACT bytes/ (caps): scan the exact bytes that will be sent -> kept free:
  /exact bytes/i in the same test, next to the mktemp and --from-file checks.

Mutation pass (scratch worktree, scripts/resolvers/redact-doc.ts): 3/3 as
expected; scanning a summary instead of the exact bytes or dropping the
Exit 3 (HIGH) branch goes red; lowering EXACT stays green. Log:
.context/mutation-redact-doc-resolver.md.

test/redact-doc-resolver.test.ts

@@ -25,7 +25,7 @@ describe("REDACT_INVOCATION_BLOCK", () => {
     const block = generateRedactInvocationBlock(ctx, ["pre-issue"]);
     expect(block).toContain("mktemp");
     expect(block).toContain("--from-file");
-    expect(block).toMatch(/EXACT bytes/);
+    expect(block).toMatch(/exact bytes/i);
   });
 
   test("encodes exit-code branches 3/2/0", () => {