Cardano Updates

Signed-off-by: Chris Gianelloni <[email protected]>

Introduce sealedTxFromLedgerTx :: Read.IsEra era => Read.Tx era -> SealedTx.
Serialises via Read.serializeTx (ledger-native) and wraps in EraValue
without any cardano-api involvement.

Migrate sealWriteTx in Transaction.Ledger.hs to use the new
constructor, pattern-matching on RecentEra to witness the era.
Removes the toCardanoApiTx -> sealedTxFromCardano' roundtrip,
dropping the Cardano.Api.Extra import from that module.

Step 2a of SealedTx decommission plan.

mithril-client-cli was only defined under pkgsMusl (x86_64-linux), leaving
darwin targets without the package and breaking devShell evaluation. Add a
native buildPackage variant for all systems where pkgsMusl is null.

fix: add glibc.bin to wrapper runtimeInputs for getconf

Bootstraps spec-driven workflow for cardano-node-antithesis:

- .specify/ scaffolding installed via nix run /code/spec-kit.
- .specify/memory/constitution.md authored from scratch, capturing
  the composer-first, SDK-instrumented, duration-robust principles
  the repo has been implicitly following since PR #53 + the
  shared/skills/antithesis-tests skill.
- .claude/commands/ speckit command definitions.
- specs/phase1-asteria-gatherer/spec.md — first feature spec:
  txpipe/asteria deployed as the eager-agent workload, one
  gatherer parallel_driver per ship, admin-bootstrap serial driver,
  anytime + finally invariants. Explicit out-of-scope list for
  phase 2+ (mine, quit, spawn contention, prize tokens).

Implements issue #56 (parent #55). No runtime changes yet; this
commit is spec-only.

fix: skip patchelf because of statically-linked esbuild binary

Add a test for ensuring that a peer can download all valid TXs when
faced with two peers with conflicting tx order.

Replace the manual segmented-witness serialization with MemoBytes,
which simplifies the code significantly. The block body is now
serialized as a flat 3-element list [invalid_transactions, transactions,
peras_certificate] instead of 5 separate segments.

Also fix PerasCert to encode/decode as bytes (matching CDDL),
reimplement alignedValidFlags using IntSet, and expose
DijkstraBlockBodyRaw/MkDijkstraBlockBody from Internal module.

Define HuddleRule instances for "block_body" and "peras_certificate"
in the Dijkstra era, with a custom CBOR generator for block_body
that generates valid transaction indices. Update the CDDL spec to
match the new block structure: block = [header, block_body].

Change genArrayTerm from Gen to MonadGen so it can be used in
CBORGen contexts (e.g. custom CBOR generators for Huddle specs).

- Add `blockBodySize` as a method on `EraBlockBody` with a default
  implementation using `EncCBORGroup`, replacing the standalone
  `bBodySize` function
- Remove `EncCBORGroup (BlockBody era)` superclass constraint from
  `EraBlockBody` so that eras can provide their own `blockBodySize`
  without needing `EncCBORGroup`

Add plain DecCBOR instances for DijkstraBlockBodyRaw and
DijkstraBlockBody (needed for decoder equivalence tests), and a
custom ToExpr instance for DijkstraBlockBody. Add block_body to
the CddlSpec test suite.