Tests: keep JSON depth safety expectations aligned with the engine error contract

The combined-main CI run https://github.com/zig-utils/zig-js/actions/runs/33204727283 failed focused-engine-tests at JSON hostile nesting is catchable. Commit 45911bd intentionally changed the shared stackGuard RangeError message to include a trailing period, but the focused JSON.parse and JSON.rawJSON assertions still require the old spelling. Both JSON parsers call that shared guard. Related security scope: #493.

Keep the catchability, RangeError type, deep array/object/mixed nesting, rawJSON, shallow-success and malformed-syntax assertions intact. Update only the stale exact-message expectations, run the complete focused runtime suite, and verify the combined-main CI gate. No depth limit, native stack or job lifecycle change is needed.

Pushed c1597fa to main: https://github.com/zig-utils/zig-js/commit/c1597fa5 . All 9 native focused runtime cases pass locally with the exact-message assertions retained. The commit changes only the two stale trailing-period expectations; no depth guard, JSON parser, lock, stack or job behavior was changed. The local run included the separate in-progress #814 class-naming candidate; combined-main CI remains the terminal check. Existing no-GIL 400/401 failure remains tracked in #722.

The corrected main commit now passes the exact CI gate that previously failed: focused-engine-tests succeeded in https://github.com/zig-utils/zig-js/actions/runs/33205914203/job/98966859194 . The complete workflow is still in progress, so this is a focused-gate success, not a claim of an all-green matrix.

Closing with terminal combined-main integration evidence: CI 33211154123 at e24c4fa completed successfully: 53 successful checks, one skipped nightly-only check, zero failed/cancelled checks. The implementation test(json): align depth guard expectations with error contract (#818) is in that revision. This completes the pending integration condition alongside the scoped local/conformance evidence recorded above. Separately discovered Error-intrinsic, Array-realm, prototype-type and restriction-path defects remain open in #823, #824, #825 and #826; this closure does not claim those are fixed.