feat(keyring,util-crypto): ML-DSA arms for createPair, alongside the curve ones

Wires @quantus/crypto into the four TYPE_* maps, so a keyring pair of type
dilithium65/dilithium87 can be created, addressed, signed with and verified.
The curve arms are untouched: quantus/common#6 removes them, but only once
post-quantum signing is proven end to end, so that a rejected first extrinsic has
two suspects rather than three.

util-crypto gains thin dilithium/ wrappers so keyring composes primitives the way
it already does for ed25519, rather than reaching into @quantus/crypto directly.

TYPE_ADDRESS is the interesting arm. Every other entry is identity or a cheap
re-encoding because on Substrate the address *is* the public key; ML-DSA takes
1952 or 2592 bytes to 32 with no way back. dilithiumVerify therefore mirrors the
runtime's Verify::verify rather than inventing anything: split sig||pk, hash the
embedded public key, check it equals the account being verified against, and only
then check the signature. Skipping the account check would accept a valid
signature from *some* key rather than *the* key, which is the whole property.

TYPE_PREFIX gets 0 for dilithium87 and 1 for dilithium65. For the curve types
those index Substrate's MultiSignature; here they index the runtime's
DilithiumSignatureScheme — a different enum reached by the same withType
mechanism, so nothing upstream of createPair needs to know.

Signing takes a mandatory context, which is quantus/common#5 arriving early
because the two are inseparable: TYPE_SIGNATURE cannot have an ML-DSA arm without
one. There is deliberately no default. Extrinsics on spec >= 148 verify under
QUANTUS_EXTRINSIC and earlier ones under the empty context, and the wrong choice
is a valid signature the chain rejects, indistinguishable locally. Only the
caller knows the spec version.

The curve sign functions are wrapped rather than passed by reference: ed25519Sign
and sr25519Sign take a third argument of their own (onlyJs), and letting it line
up with the context slot would silently reinterpret a Uint8Array as a boolean.

VRF signing refuses for ML-DSA. The construction fakes a VRF from an ordinary
signature, which is sound only given properties ML-DSA's signature does not have;
producing something that looks like a VRF proof and cannot be verified as one is
worse than refusing.

Two runtime whitelists sat behind the KeypairType union and silently rejected the
new types — the Keyring constructor and createFromJson. The compiler cannot see
those, and the first failed at construction with a message listing four types.
Both now use one named KEYPAIR_TYPES so the next change to the union has a single
place to look and the message cannot drift from the check.

Verified against quantus-cli, not against ourselves: keyring.addFromSeed with 32
zero bytes yields crystal_alice's address, signs to the runtime's wire length,
verifies under the extrinsic context and fails under the spec-147 one, and
another account's signature is rejected for it.

Refs quantus/common#2, quantus/common#5

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012uDUodEcRbBwNRi3UCmw8f

packages/keyring/package.json

@@ -23,6 +23,7 @@
   "dependencies": {
     "@polkadot/util": "14.0.3",
     "@polkadot/util-crypto": "14.0.3",
+    "@quantus/crypto": "^0.1.0",
     "tslib": "^2.8.0"
   },
   "peerDependencies": {