Summary

Adds a NIP-05 over Namecoin (.bit) resolver to @nostr-dev-kit/ndk as
a sibling to the existing DNS-based getNip05For path. Identifiers like
alice@example.bit, example.bit, d/example, and id/alice can be
resolved against the Namecoin blockchain via a caller-supplied ElectrumX
transport.

The resolver also honours the
ifa-0001
§"import" mechanism, so records that delegate shared blocks into a
sibling name (e.g. the canonical demo target testls.bit, whose apex
record is up against the 520-byte per-name limit and delegates its
nostr.names block to dd/testls) resolve correctly without the
caller having to know about the indirection. Non-import records pay
zero extra I/O.

Tracking the in-flight NIP draft and its other implementations:

• NIP draft: nostr-protocol/nips#2349
• JS sibling: nbd-wtf/nostr-tools#533
• Rust sibling: rust-nostr/nostr#1367
• Kotlin reference: vitorpamplona/amethyst
• Swift reference: nostur-com/nostur-ios-public
• Go reference: mstrofnone/nostrlib-nip05-namecoin

The parser semantics (local-part priority: exact → _ → first valid;
d/ vs id/ namespacing; tolerated leading nostr: prefix; simple
"nostr": "hex" vs extended "nostr": { names, relays, nip46 } JSON
shapes) match those references byte-for-byte.

Design choices

• Zero new dependencies. Uses the existing @noble/hashes/sha2.js
  for the ElectrumX scripthash. No nostr-tools-style additions.
• Transport-free core. NDK targets browsers, React Native, and Node;
  bundling a WSS client is undesirable. The parsing module exposes
  buildNameIndexScript, electrumScriptHash, and
  parseNameUpdateScript so callers can drive any ElectrumX transport
  they like. getNamecoinNip05For accepts an injected resolver
  function and otherwise reads ndk.namecoinResolver.
• Isomorphic. No node: imports, no import 'ws', no Node-only
  globals. TextEncoder is available on every NDK target; a manual
  encoder is provided as a fallback.
• No regressions to the DNS path. NDKUser.fromNip05 only routes
  identifiers through Namecoin when (a) the identifier matches the
  Namecoin predicate and (b) a resolver is configured. Every other
  identifier still flows through getNip05For unchanged. nip05.ts
  is untouched.

ifa-0001 "import" support

The second commit on this branch (6c4e2847) adds
expandImports, a recursive merger that handles every shape of the
spec:

• Four import value shapes — bare string, single-array,
  pair-array, canonical array-of-arrays — all normalise to the
  canonical form.
• Subdomain-selector walk via the imported value's map tree
  (exact label > * wildcard > empty default, DNS-rightmost-first).
• Importer-wins shallow merge with null as a delete marker
  (semantic suppression per ifa-0001).
• Recursion up to a configurable depth (default 4, the spec minimum);
  deeper chains are silently truncated and the importer's own fields
  are retained.
• Cycle protection via a visited (name|selector) set scoped to one
  top-level expansion.
• Lenient I/O — lookup null, throws, or malformed JSON resolve to
  {} so transient ElectrumX hiccups don't kill resolution.
• The import key is stripped from the merged result.

The expansion runs once between parsing the apex value and extracting
the nostr field, so the existing extractor sees a richer merged
object without any further changes. Non-import records short-circuit
before any lookup and cost zero extra I/O.

New public symbols

From @nostr-dev-kit/ndk:

• isValidNamecoinIdentifier / isDotBit
• NamecoinAddress (with parse, toString, electrumScriptHash)
• extractNostrFromValue, profilePointerFromRawJson
• buildNameIndexScript, electrumScriptHash, parseNameUpdateScript
• DEFAULT_ELECTRUMX_SERVERS
• getNamecoinNip05For, getNamecoinNip05User
• expandImports, DEFAULT_IMPORT_MAX_DEPTH
• Types: NamecoinResolver, GetNamecoinNip05Opts,
  NamecoinNip05Extract, ElectrumXServer,
  NamecoinImportLookup, NamecoinValue,
  NIP05_NAMECOIN_REGEX_BIT, NIP05_NAMECOIN_REGEX_NAMESPACED

On the NDK class:

• ndk.namecoinResolver?: NamecoinResolver — optional. When set,
  NDKUser.fromNip05("alice@example.bit", ndk) returns the Namecoin
  result.

Caller-side resolver shape

import {
    NamecoinAddress,
    parseNameUpdateScript,
} from "@nostr-dev-kit/ndk";

ndk.namecoinResolver = async (address) => {
    // 1. Open WSS to one of DEFAULT_ELECTRUMX_SERVERS.
    // 2. Call blockchain.scripthash.get_history with address.electrumScriptHash().
    // 3. Fetch the most recent transaction with blockchain.transaction.get.
    // 4. Decode the NAME_UPDATE output with parseNameUpdateScript and
    //    return new TextDecoder().decode(value).
    return rawJson;
};

The transport itself is intentionally left out of the npm package: it
varies per consumer (browser, React Native, Tauri/Electron) and the
ElectrumX server certificates are self-signed.

The same callback is reused for any import targets the apex value
declares — no extra wiring required on the caller side.

Tests

• core/src/user/nip05namecoin.test.ts: 34 vitest cases covering
  identifier validation, parser semantics, simple + extended JSON
  shapes (including nip46 extraction), script encode/decode
  round-trips, ElectrumX scripthash math, OP_PUSHDATA1 framing, and
  the resolver end-to-end with a mock transport.
• core/src/user/nip05namecoin-import.test.ts: 21 new vitest cases
  covering every import behaviour from ifa-0001 — all four value
  shapes, selector walks (DNS order, wildcards), importer-wins merge
  with null suppression, 4-level recursion, depth-budget
  truncation, lookup failures (null / throw / malformed JSON),
  malformed import values, cycle breaking, and the end-to-end
  testls.bit import pattern through a fake ElectrumX transport.
• bun vitest run src/user/nip05namecoin.test.ts src/user/nip05namecoin-import.test.ts
  from core/: 55 passed, 0 failed.
• Full core suite: same pass/fail counts as master — no
  regressions from this PR (the unrelated pre-existing failures in
  auth-retry, connectivity, fetchEvent-guardrails,
  ai-guardrails, and user/index exist identically on master).

Marked as draft while the NIP draft and sibling implementations
land.