Handle short inputs in gzip and wasm detection helpers

[modernzju]

Summary

This PR hardens the IsGzip and IsWasm helper functions so they return false for empty or truncated inputs instead of panicking when slicing the input buffer.

It also updates the unit tests to cover nil/short input cases and uses a minimal wasm header fixture for these magic-byte checks.

Why

Both helpers previously sliced the input before checking its length:

• input[:3] for gzip detection
• input[:4] for wasm detection

That can panic if callers pass empty data or a partially read file. Returning false is safer and matches the helpers' boolean detection behavior.

Testing

go test -v -tags "secretcli" ./x/compute/client/utils