Add Borsh serialization and Solana support

[AHartNtkn]

Problem

arm-risc0 needed Solana/Borsh support in the arm crate while preserving existing behavior for non-Solana targets. During this work, logic verification also needed to remain bound to the action-context instance.

What This PR Changes

1. Adds Solana/Borsh feature plumbing in arm.

• arm/Cargo.toml: adds optional deps (borsh, sha2, solana-program, solana-secp256k1, dashu)
• adds features:
  • borsh = ["dep:borsh"]
  • solana = ["transaction", "borsh", "dep:sha2", "dep:solana-program", "dep:solana-secp256k1", "dep:dashu"]

2. Adds Borsh support to public transaction/compliance/logic types.

• derives added across Action, ComplianceUnit, Transaction, Delta, LogicInstance, LogicVerifierInputs, ComplianceInstance, Digest, and related app-data structs
• Digest now has explicit from_bytes / to_bytes helpers used by Solana paths

3. Adds Solana-specific proving key / verification key selection and constants wiring.

• arm/src/constants.rs now gates VK bytes by feature = "solana"
• includes default (risc0-serde) and Solana (Borsh-serializing) VK constants

4. Keeps logic verification bound to action context.

• LogicVerifierInputs now carries instance_journal
• to_logic_verifier(...) decodes provided journal and checks equality against to_instance(is_consumed, root)
• returns ArmError::LogicInstanceMismatch on mismatch
• verifier now uses the provided journal bytes after validation

5. Adds Solana delta verification path.

• new arm/src/solana_delta.rs (enabled for solana without zkvm)
• verifies delta proof with Solana syscalls (hashv, secp256k1_recover) and solana-secp256k1
• includes explicit on-curve validation and accumulated delta/address matching
• extends errors with DeltaPointNotOnCurve and DeltaMismatch

6. Adds serialization support for delta proof/witness in both k256 and placeholder modes.

• Borsh impls for 65-byte DeltaProof and 32-byte DeltaWitness

Scope

Only files in this PR diff (origin/anthony/arm-dep-minimum...origin/anthony/arm-solana-support):

• arm/Cargo.toml
• arm/src/action.rs
• arm/src/compliance.rs
• arm/src/compliance_unit.rs
• arm/src/constants.rs
• arm/src/delta_proof.rs
• arm/src/delta_types.rs
• arm/src/digest.rs
• arm/src/error.rs
• arm/src/lib.rs
• arm/src/logic_instance.rs
• arm/src/logic_proof.rs
• arm/src/solana_delta.rs
• arm/src/transaction.rs
• arm_tests/arm_test_app/src/lib.rs

Verification

Ran on branch anthony/arm-solana-support.

• cargo fmt --all -- --check ✅
• cargo check -p anoma-rm-risc0 ✅
• cargo check -p anoma-rm-risc0 --no-default-features ✅
• cargo check -p anoma-rm-risc0 --no-default-features --features solana ✅
• cargo clippy --workspace --all-targets -- -D warnings ✅
• cargo test -p anoma-rm-risc0 ✅ (4 passed)
• cargo test -p anoma-rm-risc0 --no-default-features ✅ (6 passed)
• cargo test -p anoma-rm-risc0 --no-default-features --features solana ✅ (7 passed)
• Solana PA nix e2e: ./scripts/anchor-test.sh ✅ (36 passing)
  • run inside nix dev shell with PATH preferring nix toolchain wrapper:
    • export PATH="$(dirname "$(dirname "$SBF_SDK_PATH")"):$PATH"

Tracking

• Part of Integrate Different Serialization Options for Each of the Backends #203
• Companion PRs: Add EVM ABI encoding for circuit journal output #208 (EVM side), arm_circuits: add guest feature-forwarding for borsh/bin serialization #209 (arm_circuits/* guest serialization/feature forwarding)