Cardano Updates

* feat: add decode_strict to allow ledger to fail for v3 trailing bytes

Signed-off-by: yHSJ <[email protected]>

* feat: validate builtins are available

Signed-off-by: yHSJ <[email protected]>

* chore: cargo format

Signed-off-by: yHSJ <[email protected]>

* chore: address PR feedback

Signed-off-by: yHSJ <[email protected]>

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Signed-off-by: yHSJ <[email protected]>

Signed-off-by: yHSJ <[email protected]>

Implement proper flat serialization for BLS12-381 G1/G2 elements
(using compressed point format) and Data constants (via CBOR).
Previously these variants returned errors or were unimplemented.

Discharge was missing Case and Constr variants, causing incorrect
results when these terms appeared inside closures that needed
environment substitution. Also adds Arena::alloc_slice helper
used by the discharge implementation, and fixes trailing newline
in fuzz_0017 budget expectation.

Fuzzer-generated test exercising Case and Constr term discharge.
This test currently fails because discharge does not handle
Case and Constr terms.

Boolean: False accepts 1 or 2 branches, True requires exactly 2.
List: Cons accepts 1 or 2 branches, Nil requires exactly 2. Any other
branch count is an error. Previously the code was too permissive,
allowing arbitrary branch counts for lists.

Tests for case expressions on list constants:
- case-list-empty-valid: empty list with 2 branches takes nil branch
- case-list-nonempty-valid: non-empty list takes cons branch with head/tail
- case-list-empty-too-many-branches: empty list with 4 branches errors

These tests currently fail due to incorrect branch count validation
in the case-on-constants implementation.

Signed-off-by: yHSJ <[email protected]>

Signed-off-by: yHSJ <[email protected]>

Signed-off-by: yHSJ <[email protected]>

Prevents integer overflow panics when cost model inputs are very large
(e.g. dropList with a huge index). All arithmetic in costing functions,
budget subtraction, and ExBudget::Sub now uses saturating operations
so overflow produces clamped values instead of panics, letting the
out-of-budget check fire normally.

Tests that dropList with a huge integer argument fails with an
evaluation failure rather than silently overflowing the cost calculation.
This test currently fails due to integer overflow in cost arithmetic.

Adds a fuzzing harness that generates random UPLC programs and tests
them for correctness against expected evaluation behavior.