Cardano Updates

Signed-off-by: William Hankins <[email protected]>
Co-authored-by: William Hankins <[email protected]>

This commit addresses the remaining Copilot review suggestions by adding
test coverage for the new functionality introduced in PR #120.

New Tests Added:

1. Unit Tests for validateGzipFile (6 test cases)
   - ✅ Accepts valid gzip files
   - ✅ Rejects files with invalid magic bytes
   - ✅ Rejects files shorter than 2 bytes
   - ✅ Rejects empty files
   - ✅ Rejects non-existent files
   - ✅ Accepts files with correct magic bytes (validates header only)

2. Integration Test for --clean-cache Flag
   - ✅ Verifies cache is created on first build
   - ✅ Verifies --clean-cache removes and recreates cache
   - ✅ Ensures build completes successfully after cleaning

Implementation Details:

- Exported validateGzipFile from Foliage.FetchURL for testing
- Created new test module: tests/Foliage/Tests/FetchURL.hs
- Updated foliage.cabal to include:
  - New test module and dependencies
  - app/ directory in test hs-source-dirs for module access
  - Required dependencies: aeson, binary, hashable, shake, network-uri, temporary
- All 10 tests pass (6 unit + 4 integration)

Test Results:
✅ validateGzipFile: 6/6 tests pass
✅ Integration tests: 4/4 tests pass (one, --no-signatures, --write-metadata, --clean-cache)

This provides confidence that:
- Gzip validation logic works correctly and won't regress
- The --clean-cache flag operates as expected
- Cache corruption prevention features are properly tested

The gcc14 override caused a full x86_64-linux toolchain rebuild,
including glibc. The rebuilt glibc fails on Determinate Nix's Linux
VM (darwin builders) with "undefined symbol: __libc_start_main",
breaking 178+ x86_64-linux Haskell builds — far worse than the 32
Windows cross-builds the override was meant to fix.

The fixincludes issue needs a narrower solution that doesn't
invalidate all x86_64-linux derivation hashes.

Signed-off-by: William Hankins <[email protected]>

- Suppress empty witness objects in the JSON output to reduce payload size.
- Introduced an alias type to prevent infinite recursion during marshaling.

Signed-off-by: Gavin Harris <[email protected]>

Add more tests to cardano-testnet

- Added MarshalJSON method to TransactionEvent to handle Witnesses field serialization.
- Updated Witnesses field to be omitted from default JSON output.
- Introduced redeemerTagString function for converting redeemer tags to string format.

Signed-off-by: Gavin Harris <[email protected]>