Cardano Updates

Introduce 'Maybe LeiosCert' (mirrored after the existing 'Maybe PerasCert')
as an optional field on the Dijkstra-era 'BlockBody'. Other eras are
unaffected — this is the entire Leios-related ledger change per the
rebase plan's decision #3 (no 'Body'/'BodyInline'/'BodyCertificate' sum,
no early-era touch).

The change spans four pieces, all kept together so the type, codec,
hashing, and lens story land coherent:

- 'LeiosCert' / 'PerasCert' placeholders encode as @encodeListLen 0@
  rather than @encCBOR ()@ — the latter is 'encodeNull' (0xf6), which
  collides with the null-tag of 'encodeNullStrictMaybe' and made
  'SJust LeiosCert' indistinguishable from 'SNothing' on the wire.
  Adds a regression test in 'BaseTypesSpec' covering both certs.
- 'DijkstraBlockBody' carries pre-encoded bytes for body / wits /
  aux-data / is-valid / Leios cert / Peras cert, six slots total
  (numSegComponents = 6). The Leios and Peras cert slots always emit
  a CBOR token (null when absent) so the on-wire layout is fixed.
- Lens setters ('txSeqBlockBodyL', 'leiosCertBlockBodyL',
  'perasCertBlockBodyL') rebuild via the bidirectional
  'DijkstraBlockBody' pattern. The previous setters only updated the
  structural field and silently kept the stale pre-encoded bytes, so
  e.g. setting txs left 'dbbTxsBodyBytes' as the empty list and the
  block on the wire had no transactions even though the in-memory
  rep was correct. Mirrors the Alonzo idiom
  @lens abbTxs (\_ s -> AlonzoBlockBody s)@.
- 'Arbitrary' and 'TreeDiff' instances for the body extended to
  generate / show the new cert slot.

Co-Authored-By: Claude <[email protected]>

The Leios prototype rebase doesn't need 'cardano-ledger-canonical-state',
'cardano-ledger-conformance', 'cardano-ledger-test', 'plutus-preprocessor',
'ledger-state', or 'cardano-ledger-repl-environment'. They depend on
'cardano-cls', whose source-repository-package isn't trivially compatible
with this base — comment them out so the rebase builds cleanly while we
focus on Leios scope.

Co-Authored-By: Claude <[email protected]>

Re-authored on top of c175b1b317 (the cardano-ledger commit compatible
with consensus main's CHaP index-state 2026-04-13) to match the older
fat-constructor DijkstraBlockBody shape (pre-memoization refactor).
Equivalent to b6b2feb006 on leios-prototype-remake, which targeted the
post-memoization shape (DijkstraBlockBodyRaw + lensMemoRawType).

Adds:
* `dbbLeiosCert :: StrictMaybe LeiosCert` field and matching
  `dbbLeiosCertBytes :: Maybe BSL.ByteString` byte-cache, mirroring the
  PerasCert pattern in this older shape.
* `LeiosCert` placeholder newtype over ByteString with derived
  EncCBOR/DecCBOR/NoThunks/NFData (the real type lands with the Leios
  voting machinery).
* `leiosCertBlockBodyL` lens method on `DijkstraEraBlockBody`.
* Pattern synonym extended with a third `StrictMaybe LeiosCert` arg;
  body threads the bytes through `hashDijkstraSegWits` (now takes the
  Leios bytes arg too).
* `EncCBORGroup` appends the optional Leios cert bytes after the
  optional Peras cert bytes.
* `DecCBOR` handles three list-length cases: 4 (neither), 5 (Peras
  only, legacy), 6 (Peras + Leios). A Leios-only encoding is not
  expressible without ambiguity at len 5 \-- intentional: Dijkstra-era
  blocks aren't on the wire yet.
* `NoThunks` `AllowThunksIn` list extended with `dbbLeiosCertBytes`.
* Testlib: `Arbitrary LeiosCert` (and `DijkstraBlockBody <*> arbitrary
  <*> arbitrary <*> arbitrary`); `ToExpr LeiosCert` and updated
  `ToExpr (DijkstraBlockBody era)` constraint set.

Only the Dijkstra era is Leios-enabled \-- earlier eras are untouched.

Verified: `cabal build cardano-ledger-dijkstra:lib:cardano-ledger-dijkstra`
and `cabal build cardano-ledger-dijkstra:lib:testlib` both clean.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

feat/refactor: probabilistic light client extracted module

Resolves #634

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

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

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