Cardano Updates

Two runnable connect, balance, and send starters under examples/templates (evolution-vite-react, mesh-nextjs-template), one per SDK, that back the Build a dApp walkthrough. Both build with npm run build; the Mesh one needs a libsodium-wrappers-sumo override and a polyfill next.config to compile under the current Mesh release.

Add a tool-agnostic Your first dApp walkthrough with even Evolution and Mesh tabs from scaffold to send, each backed by a runnable template, rework the scaffolding stub to point at the templates, and surface the walkthrough from the module overview.

Documentation for those running a node in the testnet, includes how to setup a stake pool. It uses the tagged prototype.

Signed-off-by: Akhil Repala <[email protected]>

mainnet keeps the Mithril snapshot policy (base default); the test
networks override LedgerDB.Snapshots with an explicit options object: the
per-network SnapshotInterval (preview 864, preprod 4320) plus the full set
of snapshot options (SlotOffset 0, RateLimit 600, MinDelay 300, MaxDelay
600, NumOfDiskSnapshots 2). Closes the last parsed network-divergence gap.

Confirmed against cardano-node: its parser (Cardano.Node.Configuration.POM)
reads only LastKnownBlockVersion-Major/-Minor/-Alt and never
MaxKnownMajorProtocolVersion (which appears in no node Haskell source). It
is a dead key the node ignores, so cardano-config intentionally does not
parse it.

Confirmed against cardano-node: its parser (Cardano.Node.Configuration.POM)
reads only LastKnownBlockVersion-Major/-Minor/-Alt and never
MaxKnownMajorProtocolVersion (which appears in no node Haskell source). It
is a dead key the node ignores, so cardano-config intentionally does not
parse it.

mainnet keeps the Mithril snapshot policy (base default); the test
networks override LedgerDB.Snapshots with an explicit options object: the
per-network SnapshotInterval (preview 864, preprod 4320) plus the full set
of snapshot options (SlotOffset 0, RateLimit 600, MinDelay 300, MaxDelay
600, NumOfDiskSnapshots 2). Closes the last parsed network-divergence gap.

- A section value may now be a list of paths/objects, deep-merged in
  order so a later entry overrides an earlier one (e.g.
  ["Network.variants/Network.relay.json"]); nested objects merge
  recursively.
- The package's base default defaults/<Component>.json is always read as
  the bottom layer and the user's section layer is merged on top, so a
  config can name only a variant and still inherit the base defaults.
- Move the opt-in variant files into defaults/<Component>.variants/.
- Expose the data dir via Paths_cardano_config; add an example and a test
  asserting later-overrides-earlier.

LedgerDB.Snapshots defaults to Mithril and LedgerDB.QueryBatchSize to
100000 (from ouroboros-consensus), so they are resolved rather than
optional. The mempool timeouts have no node default (the node applies no
timeout), so they stay optional and are intentionally absent here.

Move the generated schema into schemas/ alongside one schema per
component, and assert in the test-suite that every committed schema
(whole + each component) matches the codecs, so none can drift. Add
scripts/gen-schemas.sh to regenerate them.

Give Network, LocalConnections, Mempool and Testing the f parameter (as
Storage/Consensus/Protocol already had), so NodeConfiguration carries
Identity-wrapped components and is complete by construction. A field
becomes f a when it has an always-applied base default and stays Maybe
when 'unset' is a valid state. Each component gains a finalize that turns
the merged partial form into Identity (erroring, via requireField, if a
base default is missing); resolveConfiguration runs them and reports
failures as ConfigResolutionError. Add a resolveConfiguration test.

Also rename the envelope keys to { Version, Configuration } and fix the
README (any component can be a sub-file/list; HermodTracing should point
at a tracing file relative to the config).

Introduce a new `cardano-config` library that provides a single
entry-point for parsing the `cardano-node` configuration.

It defines:

- A CLI options parser based on `optparse-applicative` (`parseCliArgs`).
- JSON/YAML parsing of the configuration files, derived from
  `autodocodec` codecs (`parseConfigurationFiles`).
- `resolveConfiguration`, combining both into a `NodeConfiguration`.

The configuration keys are grouped into components (Storage, Consensus,
Mempool, Network, Protocol, Testing, Tracing). A bundled
`cardano-config-schema` executable dumps the JSON Schema derived from the
same codecs as the authoritative key listing.

Register the package in `cabal.project`.

Reference RFC 3986 (URI authority, bracketed IPv6) as the rationale and
RFC 5952 for the address text form, and note that the RFC 5321 SMTP
address-literal form is intentionally not accepted.

cardano-config is the origin of one defaults file per component, applied
as the base layer during resolution. Each component is ultimately owned
by its implementing layer, which will adopt these and keep them aligned
via CI. Values confirmed from ouroboros-network are included; the rest
are left unset for the owning layer to fill (see defaults/README.md).
Genesis files are intentionally not defaulted (network-specific).