Cardano Updates

 shared-consensus: extract 'pure' consensus core, adopt in sim-rs and net-rs, add UI display of EB announcement & certification, fix state leak and O(N) CPU growth issues in net-node.

The `shared_consensus` adapter still called pre-chain-tree
signatures on `PraosState` and constructed an incomplete
`ChainTipContext`:

- `register_self_produced` and `on_block_received` now take a
  `tx_count: u32`; sourced from `rb.transactions.len()`.
- `ChainTipContext` now requires `tip_rb_slot: Option<u64>`;
  populated via `praos.adopted_tip_rb_slot()` so sim-rs's
  shared-consensus variant benefits from the chain-progress prune.

55 sim-rs tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

fix: Redeemer map behavior to match Haskell impl

`peek_unannounced_for_peer` ran a full mempool scan with a
`BTreeSet::insert` per tx, unconditionally cloning each tx_id.  At
steady state (10k-tx mempool, 5 peers, ~25 admits/sec) it pegged a
release-mode `perf` profile at 66% in `BTreeMap::insert` — the
dominant CPU consumer driving the cluster into saturation around
block 70.

Two changes:

1. `peek_unannounced_for_peer` now `contains`-checks before the
   `clone-and-insert`, eliminating the per-tx heap allocation for the
   majority of tx ids the peer has already seen.  Still O(N) but no
   longer allocator-bound.

2. The admit-fanout path is now point-to-point.  `Mempool` carries
   an `mpsc::Sender<PendingTx>` (cap 1024); `push` `try_send`s the
   just-admitted tx, the main loop's receive branch announces it to
   each connected peer via `MempoolState::mark_announced_to_peer`
   — a single `BTreeSet::insert` per peer instead of a full mempool
   rescan.  Overflow falls back to the pull path: the tx remains in
   the mempool, peers see it on their next `MsgRequestTxIds`.

`merge_eb_body` no longer signals the admit channel — EB-pinned
bodies live outside the free pool that TxSubmission iterates, so
there's nothing for the fan-out to do; LeiosFetch BlockTxs carries
that data.

Verified live: cluster runs past block 60 single-tip with CPU
flat at ~10% per node.  118 net-node tests + 269 shared-consensus
tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

making all tests that use reqwest fails if run without any other crate
that define a backend.

And `ImmutableDigester::compute_digest`, allowing removal of the network
parameter from the `CardanoImmutableDigester`.

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