fix: removing reduntant decode in prove

[mrzeszutko]

Summary

Eliminates redundant encode/decode cycle during internal proof verification in AztecClientBackend.prove().

Before: When prove() generated a proof, it would:

1. Encode the proof to msgpack bytes
2. Call verify() which immediately decodes those bytes back
3. Pass the decoded proof to chonkVerify() which encodes again

After: prove() now calls a private verifyNative() method that accepts the native ChonkProof directly, skipping the unnecessary encode/decode round-trip.

This reduces conversions from 4 to 2 for internal verification with no impact on the public API.

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 3 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/7b17756ca370b2ec�7b17756ca370b2ec8;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_epochs/epochs_invalidate_block.parallel.test.ts "committee member invalidates a block if proposer does not come through" (95s) (code: 1) group:e2e-p2p-epoch-flakes (\033Michal Rzeszutko\033: Removing reduntant decode in prove)
\033FLAKED\033 (8;;http://ci.aztec-labs.com/5700b5b9a1cf0476�5700b5b9a1cf04768;;�): yarn-project/scripts/run_test.sh prover-client/src/proving_broker/proving_broker.test.ts (32s) (code: 1) (\033Michal Rzeszutko\033: Removing reduntant decode in prove)
\033FLAKED\033 (8;;http://ci.aztec-labs.com/1d1f74fee76d4f75�1d1f74fee76d4f758;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_epochs/epochs_invalidate_block.parallel.test.ts "proposer invalidates multiple blocks" (604s) (code: 124) group:e2e-p2p-epoch-flakes (\033Michal Rzeszutko\033: Removing reduntant decode in prove)