feat(loaders): add NIP-05 over Namecoin (.bit) identity loader

[mstrofnone]

NIP-05 over Namecoin (.bit) identity loader

This PR adds a transport-free helper module and matching loader for resolving
NIP-05 identifiers rooted in the Namecoin blockchain
(the .bit TLD), rather than DNS. It is the loaders-package companion to the
existing DnsIdentityLoader / dns-identity helper — same shape, different
root of trust.

Spec draft: nostr-protocol/nips#2349.

Design siblings already in flight in other Nostr ecosystems:

• JS / nostr-tools: nbd-wtf/nostr-tools#533
• Rust / rust-nostr: rust-nostr/nostr#1367

The parser shape (local-part priority exact → _ → first valid, d/
vs id/ namespace handling, leading nostr: prefix tolerance, simple
nostr: "<hex>" vs extended nostr: { names, relays, nip46 } form) is
ported from those references, themselves ports of the Kotlin implementation
in Amethyst and the Swift port
in Nostur.

What's added

packages/loaders/src/helpers/namecoin-identity.ts:

• parseNamecoinAddress(input) — accepts <x>.bit, alice@<x>.bit, d/<x>,
  id/<x>, with optional leading nostr: prefix
• isNamecoinIdentifier / isDotBit — cheap front-door checks
• extractNostrFromValue(address, json) — extracts pubkey + optional relays +
  optional nip46 relays from a Namecoin name value, matching the reference
  local-part priority rules
• getIdentityFromNamecoinValue — builds an Identity (the existing
  dns-identity type) keyed by the Namecoin name in domain
• expandImports(value, lookup, maxDepth = 4) — recursively resolves
  ifa-0001 "import" directives so apex records that delegate the
  nostr.names block to a sibling name (the canonical testls.bit
  workaround for the 520-byte per-name limit) merge correctly before the
  nostr field is extracted. Supports the canonical array-of-arrays form
  plus the three real-world shorthand forms (bare string, single-element
  array, name+selector pair), null semantic suppression, the DNS-dotted
  subdomain selector walk through the imported map tree (exact → * →
  "" fallback), the spec-mandated minimum recursion depth of four,
  visited-set cycle protection, and best-effort handling of failed
  sub-lookups so transient ElectrumX hiccups never nuke an otherwise
  resolvable record. Records without an "import" key pay zero extra I/O.
• buildNameIndexScript / electrumScriptHash / parseNameUpdateScript —
  Namecoin script + ElectrumX scripthash helpers for callers that drive the
  ElectrumX query themselves (handles direct push, OP_PUSHDATA1,
  OP_PUSHDATA2, and OP_PUSHDATA4 framing)
• DEFAULT_ELECTRUMX_SERVERS — the same three operator pairs the Kotlin /
  Swift / Rust references ship

packages/loaders/src/loaders/namecoin-identity-loader.ts:

• NamecoinIdentityLoader mirroring DnsIdentityLoader's observable surface
  — same cache?: AsyncIdentityCache, same expiration / dedupe semantics,
  same Identity return shape
• A single transport hook loader.resolve = (namecoinName) => Promise<string>
  that the consumer wires up to an ElectrumX (WSS / TCP+TLS) client of their
  choice. The default implementation throws a clear error so misconfiguration
  is loud rather than silent.
• An importDepth knob (default 4, the ifa-0001 minimum) that controls the
  import-chain recursion depth. Set to 0 to disable import-following
  entirely.

Why transport-free

applesauce-core and applesauce-loaders need to stay isomorphic — no
import 'ws', no node: imports, no pinned self-signed certificates. The
helpers do all the parsing / verification and the loader stitches in
caching and dedupe, but the actual ElectrumX WSS / TCP+TLS connection is
left to the consumer (browser, Tauri, Node, Bun, etc. all have different
preferences). This matches how nostr-tools/nip05namecoin is being shaped
in the upstream JS sibling PR.

Runtime deps

One small addition to applesauce-loaders/package.json:

   "dependencies": {
+    "@noble/hashes": "^1.7.1",
     "applesauce-core": "^6.1.0",
     ...
   }

@noble/hashes is already a direct dep of applesauce-relay and
applesauce-wallet-connect at the same ^1.7.1 range, and already
transitively present via nostr-tools. Used solely for sha256 in
electrumScriptHash. No other new runtime deps.

Tests

60 new tests across two files:

• packages/loaders/src/helpers/__tests__/namecoin-identity.test.ts — 40
  tests covering parser positive/negative cases, the nostr: prefix, the
  simple vs extended JSON forms, the _ and first-valid fallbacks for
  domain vs identity namespaces, Identity construction, script layout,
  scripthash reversibility, OP_PUSHDATA1 framing, and the full
  expandImports matrix (all four "import" shapes, selector walk +
  wildcard, importer-wins, null suppression, depth-4 happy path,
  depth-truncation, cycles, malformed-input + lookup-failure lenience)
• packages/loaders/src/loaders/__tests__/namecoin-identity-loader.test.ts
  — 20 tests covering the default-resolver error, extended/simple JSON
  parsing, error/missing branches, cache hit/miss/expired, the
  single-identifier overload, concurrent-request dedupe via the
  requesting map, end-to-end import-chain resolution of bare and named
  .bit identifiers, the zero-extra-cost guarantee for non-import
  records, importer-wins on the nostr.names map, graceful degradation
  when the imported sibling is unreachable, and the importDepth = 0
  disable knob

pnpm --filter applesauce-loaders test: 139/139 (was 79; 60 new).
pnpm --filter applesauce-core test: 562/562.

Snapshot updates

packages/loaders/src/helpers/__tests__/exports.test.ts and
packages/loaders/src/loaders/__tests__/exports.test.ts regenerated to
include the new symbols (DEFAULT_IMPORT_DEPTH, expandImports).

Files touched

.changeset/nip05-namecoin.md                                      (new)
.changeset/nip05-namecoin-import-chain.md                         (new)
packages/loaders/package.json                                     (+1 dep)
packages/loaders/src/helpers/index.ts                             (+1)
packages/loaders/src/helpers/namecoin-identity.ts                 (new, ~650 lines)
packages/loaders/src/helpers/__tests__/exports.test.ts            (snapshot)
packages/loaders/src/helpers/__tests__/namecoin-identity.test.ts  (new, ~440 lines)
packages/loaders/src/loaders/index.ts                             (+1)
packages/loaders/src/loaders/namecoin-identity-loader.ts          (new, ~220 lines)
packages/loaders/src/loaders/__tests__/exports.test.ts            (snapshot)
packages/loaders/src/loaders/__tests__/namecoin-identity-loader.test.ts (new, ~270 lines)

Out of scope

• No DNS-identity changes — dns-identity.ts / dns-identity-loader.ts
  are untouched; this is purely additive
• No ElectrumX client / WSS transport (intentionally consumer-owned)
• No applesauce-core helper barrel for Namecoin — the parser lives in
  applesauce-loaders/helpers only (the upstream nostr-tools sibling
  is still in PR; once that lands, a thin core re-export can follow)

Draft until the upstream JS sibling settles, but the API is intended to be
stable as-is.

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Latest commit: 9968f5a

The changes in this PR will be included in the next version bump.

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applesauce-loaders	Minor

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