fix(capi): use as_ref() null-check idiom for error pointer deref in test (#2404)

Closes CodeQL rust/access-invalid-pointer #35.

Before: test asserted `!error.is_null()` then performed raw deref
`(*error).message`. CodeQL does not model `assert!` as a guard, flagged
invalid-pointer deref.

After: `error.as_ref().expect("ffi_boundary must set error").message`.
Same semantics (aborts if null), no raw deref, idiom the query
understands.

Proof: `cargo fmt --check -p bashkit-capi` clean, `cargo clippy -p
bashkit-capi --all-targets` 0 warnings, `cargo test -p bashkit-capi`
green (1 + 19 passed).

Note: alerts #9/#12/#13 (napi struct lines) and the 13 hard-coded-crypto
test-key alerts triaged as false positives, no code change.

Author: chaliy

Cargo.lock

@@ -947,8 +947,10 @@ mod tests {
             });
 
             assert_eq!(status, BashkitStatus::InternalError);
-            assert!(!error.is_null());
-            assert_eq!((*error).message, b"internal error");
+            assert_eq!(
+                error.as_ref().expect("ffi_boundary must set error").message,
+                b"internal error"
+            );
             bashkit_error_free(error);
         }
     }

crates/bashkit-capi/src/lib.rs

@@ -1657,7 +1657,7 @@ version = "1.1.4"
 criteria = "safe-to-deploy"
 
 [[exemptions.rustls]]
-version = "0.23.43"
+version = "0.23.45"
 criteria = "safe-to-deploy"
 
 [[exemptions.rustls-native-certs]]