feat: introduce stateless Mantle transaction validation

[aimendj]

This PR splits Mantle transaction validation into two stages: stateless validation at ingress for structural checks and cryptographic verification, and stateful validation during ledger execution for state-dependent checks and mutations. This avoids repeating expensive signature and zkSNARK verification, moves PoC verification into the Mantle layer, adds defense-in-depth checks, and wires stateless validation into block ingress with clearer error handling.

[github-actions]

Unit Test Results

       5 files  ±  0     690 suites   - 5   1m 5s ⏱️ ±0s
   655 tests +13     642 ✔️ +13  13 💤 ±0  0 ❌ ±0 
3 405 runs  +35  3 340 ✔️ +35  65 💤 ±0  0 ❌ ±0 

Results for commit df55f3e. ± Comparison against base commit 333c4d0.

This pull request removes 16 and adds 29 tests. Note that renamed tests count towards both.

ChannelTransfer op with wrong proof kind → InvalidProof
LeaderClaim op wired through LedgerState
Transfer op with wrong proof kind → InvalidProof
configurationThreshold == 0 → InvalidChannelConfig
configurationThreshold > keys.len → InvalidChannelConfig
duplicate input NoteId → DoubleSpend
empty keys → InvalidChannelConfig
no inputs → EmptyInputs
ops/proofs count mismatch → InvalidProof
rejects invalid proof
…

ChannelConfig: rejects configurationThreshold > keys.len
ChannelConfig: rejects empty keys
ChannelConfig: rejects zero configurationThreshold
ChannelConfig: rejects zero transferThreshold
ChannelDeposit: rejects duplicate inputs
ChannelDeposit: rejects empty inputs
ChannelInscribe: verifies Ed25519 signer signature
ChannelTransfer: rejects duplicate inputs
ChannelTransfer: rejects empty inputs
ChannelTransfer: rejects zero-value output note
…

♻️ This comment has been updated with latest results.